One of the subjects in Luther studies that I've addressed over the years is Luther's view on Mary's Sinlessness. Sure, dull stuff to most. It's the Roman Catholic side that finds this a subject worthy of study: anything that even looks like a pro-Mary Romanist quote is fine, with or without a context.
Even Wikipedia is weighing in the issue:
In the course of his life Luther made contradictory statements about Mary's immaculate conception. For example, in 1532 Luther says that Mary was conceived in sin, in 1544 he says: 'God has formed the soul and body of the Virgin Mary full of the Holy Spirit, so that she is without all sins, for she has conceived and borne the Lord Jesus.' Elsewhere, "All seed except Mary was vitiated [by original sin]." When concentrating specifically on Mary herself as the Mother of God, Luther acknowledges God's singular action in bringing her into the world, but in making general comments about the universality of human sinfulness, he includes her among all the rest of humanity.
"Mother Mary, like us, was born in sin of sinful parents, but the Holy Spirit covered her, sanctified and purified her so that this child was born of flesh and blood, but not with sinful flesh and blood. The Holy Spirit permitted the Virgin Mary to remain a true, natural human being of flesh and blood, just as we. However, he warded off sin from her flesh and blood so that she became the mother of a pure child, not poisoned by sin as we are. For in that moment when she conceived, she was a holy mother filled with the Holy Spirit and her fruit is a holy pure fruit, at once God and truly man, in one person."
 Martin Luther, D. Martin Luthers Werke, Kritische Gesamtausgabe, 61 vols., (Weimar: Verlag Hermann Böhlaus Nochfolger, 1883-1983), 52:39 [hereinafter: WA]
 WA, 39, II:107.
 Sermons of Martin Luther, 291
I don't know enough about Wikipedia to determine who, or whom writes articles like this. It would be interesting to know. It is true Luther did make puzzling comments about Mary's sinlessness or lack thereof throughout his life. I've put up a lot of blog entries on Luther's Mariology in the past. Overall, Wiki made the right conclusion, though footnote #19 should have been: Sermons of Martin Luther, Vol. 3, ed. John Nicholas Lenker. (Grand Rapids: Baker Books, 1996), 291.
Recently though I came across a number of statements from The Complete Sermons of Martin Luther 1:2 (Michigan: Baker Books, 2000) to add to the list. Luther makes a number of comments on Luke 2, when the parents of Jesus lost him. I've documented one these sermons before. Here are some other quotes (with contexts that can be produced!) to add to the list:
13. The words of Luke "and they understood not the saying which he spake unto them" are especially to be noted here. With these words he silenced the idle talk of those who exalted and praised the Virgin Mary too highly, asserting that she knew everything and could not err. For you see here how the Lord permits her to seek her child for a long time in vain, till she finds him in the temple after three days. In addition to this, Jesus seems to reprimand her when he says: "How is it that ye sought me? knew ye not that I must be in my Father's house?" She understood not the saying which he spake to her. Consequently all the idle talk to which we have referred is nothing but falsehood, and the Virgin Mary does not need this fabricated and mendacious praise. God concealed much from her and led her through many trials, so that she might remain humble and not think herself better than others. [Sermons of Martin Luther 1:2, p.23]
18. Therefore we should reply to this from the Gospel, as I said: Even if Mary, the Holy Virgin, had done this, it would not be surprising if she had erred. She was the mother of God, and yet she did not know where to find Christ; she sought him among her kinsfolk and acquaintance and failed to find him. Now if she did not succeed in finding Christ among her kinsfolk, but had finally to come to the temple, how shall we expect to find him outside of the Word of God in human doctrines, in the decrees of the councils or the teachings of the scholastics? Bishops and councils have undoubtedly not possessed the gift of the Holy Spirit in as large a measure as Mary. If she erred, why should not they also be mistaken who fancy to find Christ elsewhere but in his Father's house, that is in the Word of God? [Sermons of Martin Luther 1:2, p.25]
22. But, they say, the Christian church is always led by the Holy Spirit, who will not permit the church to err or go wrong. To this we answer with what we said before: However good the church may be, it has never possessed the Spirit in as large a measure as Mary, who although she was led by the Spirit, erred nevertheless, so that we might learn from her experience. If she herself is uncertain, how can you make me certain? Whither should we then go? We must also come into the temple, that is to say we must cling to the Word of God, which is secure and will not fail us and where we will certainly find Christ. I must therefore always be with the Word, if I cleave to it. If the Word of God goes conquering through death and remains alive, I must also pass through death to life, and nothing can hinder or destroy me, neither sin nor death, nor the devil. The comfort and boldness I derive from the Word of God cannot be engendered by any other doctrine, for none can be compared with it. [Sermons of Martin Luther 1:2, p.27]
27. There are many similar examples and types elsewhere in the Gospel which point out the same truth, namely, that nothing should be taught but the Word of God and no other doctrine should be accepted, because Christ can be found only in the Scriptures. Thus we read in the Gospel for Christmas, Lk 2, 12, where the angel, who announced the birth of Christ, said to the shepherds: "And this is the sign unto you: Ye shall find a babe wrapped in swaddling clothes, and lying in a manger." Why does he not direct them to Mary and Joseph, but only points them to the swaddling clothes and the manger? The reason is that God will not point us to any saint, not even to the holy mother herself, for they may all err. Therefore a special place must be pointed out where Christ is, namely the manger, where he surely may be found, even if Joseph and Mary were not present. This signifies that Christ is completely wrapped in the Scriptures, just as the body is wrapped in the clothes. The manger is the preaching of the Gospel, where he is lying and where he is apprehended, and from which we take our food. Now it would indeed appear that the child should lie where Joseph and Mary are, these great and holy people. Yet the angel points only to the manger, which he will not have overlooked or dishonored. It is an insignificant and simple expression, but Christ is found in it. [Sermons of Martin Luther 1:2, p.29]
30. Let us then be prepared for their representations and expostulations to the effect that the Christian church can not err, so that we may know how to meet them, and say: Here is not the word of man, but the Word of God. We read in this Gospel that his mother, Mary, was filled with the Holy Spirit, and yet she erred. Likewise we read in the Acts that there was a Christian council of such who believed and who had the Spirit, and yet they stumbled and would have established an unchristian law, if others had not protested. We should therefore not believe any council or ;saint, if they come without the Word of God. This is then the sum total of this Gospel, and if anything else is to be said on it, we will let those explain it who have leisure; but he who studies it faithfully, will easily understand it.[Sermons of Martin Luther 1:2, p.30]
8. The affliction and suffering she was compelled to endure were not of a nature that they had occurred without her fault, but her conscience forced her to remember how God had entrusted the child to her and that no one else was accountable for him, and hence storms burst and thundered in her heart: Behold, thou hast lost the child. This is no one's fault but thine own; for thou shouldst have waited on him and looked after him, and not permitted him for` a moment to go out of thy sight. How wilt thou give an account of this before God, since thou hast failed to watch over him? This is the result of sin and thou art no longer worthy to be his mother; yea, thou hast deserved to be condemned by him before all people, inasmuch as he has conferred on thee the great honor and favor of choosing thee for his mother.
9. Should not her heart have failed and fainted here from anxiety, for two reasons? First, because she lost her son and was unable to find him; secondly, which was the most severe of all and which could not happen to other mothers, making the pain all the more severe, because she must abhor herself before God, the only Father of the child, that he would no longer have or regard her as his mother, and hence she must be more sorrowful and sad at heart than any other woman on earth. In her own heart she regards herself guilty of the same sin as Eve, the first mother, who brought the whole human race to ruin. For what are all sins compared with this one, that she has neglected and lost this child, the Son of God and the Saviour of the World? And if he should not be found, or, since he could not be lost, if God should have taken him back to himself, she would be the cause of preventing the completion of the work of the redemption of the world. Such and doubtless many other thoughts filled her heart with great fear, especially since she, as a pious child of God, had a very tender heart and conscience. [Sermons of Martin Luther 1:2, p.35-36]
32. This should shut the mouths of vain babblers who exalt the holy Virgin Mary and other saints as if they knew everything and could not err; for you can see here how they err and falter, not only in this that they seek Christ and know not where to find him until they accidentally come to the temple, but also that they could not understand these words with which he censured their ignorance and is compelled to say to them: “Knew ye not, that I must be in the things of my Father?” The Evangelist has pointed this out with great diligence, in order that men should not give credence to such falsehoods as ignorant, inexperienced and conceited teachers of works righteousness present in exalting the saints, even setting them up as idols. [Sermons of Martin Luther 1:2, p.45]
34. Examples like this are useful and necessary to show us that even the saints, who are the children of God and highly favored above others, still have weaknesses so that they frequently err and blunder, yea, retain many faults, at times even commit great sins; yet not intentionally and willfully, but from weakness and ignorance, as we see again and again in the lives of the apostles. This happens in order that we may learn neither to build nor depend on any man; but, as this Gospel teaches, to cling to the Word of God only; and in order that we may find comfort in such examples and be not led to despair, although we may be weak and ignorant; and yet that we should not become bold and carnally secure on account of such grace as the haughty and pretended saints are wont to do.[Sermons of Martin Luther 1:2, p.46]
35. In a word, you have in this Gospel a strong example with which to overthrow the common cry both of the false saints and the great critics, which they still keep up, in order that contrary to the Word of God they may continue in their trifling; to wit, that they may reproach us with the writings and teachings of the fathers and the decrees of the church and councils; for, they say, these had the Holy Spirit, therefore they could not err, etc. In this way they desire to mislead us concerning the Scriptures and the true place to which Christ himself points and where he can surely be found; in order that what happened to Mary the mother, and to Joseph may happen also to us, namely, that we seek Christ everywhere and yet find him nowhere except at the place where he is to be found. The same thing has been carried on with great power in Christendom through the cursed government of the pope, who has striven both by his teachings and actions, threats and punishments to cause men to fail in seeking or finding Christ in the Scriptures. [Sermons of Martin Luther 1:2, p.46]
38. ...[T]hey have abandoned Holy Scripture; yet so as to attach it to some of the writings and expositions of the fathers, nevertheless not any farther than it pleased the pope and would not prove contrary to his law, and that no one should use Scripture except in accordance with the pleasure of the pope, to whom alone pertains the interpretations of Scripture and whose knowledge and judgments every one is bound to accept. Yet, in spite of this, they so far honor the fathers as to demand that their interpretations and explanations should be followed. All the world accepted this and so received all that the fathers said, as if they could not err, and shouted again: Aye, how could it be possible that so many holy, learned and highly intelligent men should not have understood the Scriptures?
39. To this we should reply as is taught in this Gospel: Be they called holy, learned, fathers, councils, or any other name, even though they were Mary, Joseph and all the saints it does not follow that they could not have erred and made mistakes. For here you learn that the mother of Christ though she possessed great intelligence and enlightenment, showed great ignorance in that she did not know where to find Christ, and in consequence was censured by him because she did not know what she should have known. If she failed and through her ignorance was brought to such anxiety and sorrow that she thought she had lost Christ, is it a wonder that other saints should often have erred and stumbled, when they followed their own notions, without the guidance of Scripture, or put their own notions into Scripture.[Sermons of Martin Luther 1:2, p.48]
46. You say further: Yea, the church and the fathers were endowed with the Holy Spirit, who kept them from error. The answer to this is not difficult: The church and councils may have been ever so holy, they did not have the Holy Spirit in greater measure than Mary, the mother of Christ, who was also a member, yea, at the time, the most eminent member of the Church. And although she had been sanctified by the Holy Spirit; yet he permitted her at times to err, even in the important matters of faith. From this it does not follow, that the saints, who were endowed with the Spirit, could on this account not err, nor that everything they said would have to be correct. Great weakness and ignorance may be found to exist even in the most eminent people and hence we cannot judge concerning doctrines and matters of faith on the basis of personal holiness, for all this can fail. But here you come to the Word of God which is sure and infallible, where you shall certainly find Christ and the Holy Spirit, and can be and remain firmly fortified against sin, death, and the devil.[Sermons of Martin Luther 1:2, p.50]
49. This is also given for our admonition, in order that we may endeavor to keep the Word of God in our hearts, as the blessed Virgin did, who, seeing she had erred and lacked understanding, became all the more diligent to keep in her heart all she heard from Christ. She furnishes another example, that above all things we should adhere to the Word and not permit it to go out of our hearts, but constantly use it, learn to gain strength from it, find comfort in it, and increase in it, as is indeed necessary for all of us. For when we come to the point where we shall be tried and tempted, we are liable to be. forgotten or dropped even by those who are diligent. [Sermons of Martin Luther 1:2, p.52-53]