Infallibility of the prophets in Islam???

This post is more of a question than commentary. In various khutbahs (the Islamic version of a sermon delivered at Friday prayer), I've heard some comments about the various prophets that almost make me think that the prophets are infallible and don't make mistakes or sin. Although they are indeed guided and inspired by God, their humanity still dictates their imperfection. The Quran mentions Adam's fall from grace in the Garden of Eden and also mentions Moses' (Moosa, in Arabic) murder of an Egyptian slave driver, although those are the only mentions I recall of prophets' mistakes. These are proof to me that Islam doesn't propose their infallibility. However, as I've said, I've heard comments that make me think otherwise so I figured I'd pose my question here.

Christianity definitely accepts that the prophets were imperfect men and sinned. In the Bible, there are stories of Adam's fall, Noah's drunkenness, David's adultery, Moses' murdering, and I'm sure more. The prophets were guided and inspired by God but at the same time, they were flawed human beings. The only man claimed to be free from sin was Jesus because of his being simultaneously God and man. His human side was tempted but he resisted and remained sin free.

However, I've heard Muslims get offended at the prospect of David's adultery or Noah's drunkenness. Does Islam preach the perfection of prophets? I don't see how that could be considering the Quran's inclusion of Adam's fall and Moses' murdering. Does Islam claim that Muhammad was sinless? I don't think accepting his sin would have any affect on the religion. He could easily be divinely guided when delivering the Quran without error yet still be an imperfect, flawed man. Just because he as a man is flawed doesn't mean the Quran would have to be flawed.

As I said, I don't know what Islam's stance is on this subject. If anyone knows, please inform me. If not, I guess I'll just have to do more research on my own.

As promised, prophecies

I've read some of the Old Testament prophets in full and I'm sure I've encountered all of their juciest bits somewhere between church and my own readings. Judaism holds that the prophets foretold of the Messiah, who will come restore the temple in Jerusalem, restore God's chosen people to their seat of glory, and bring about God's will on Earth. Both Christianity and Islam believe that Jesus was the Messiah, whereas Judaism obviously insists that Jesus did not fulfill the messianic prophecies. Islam goes one step farther and believes that the Old Testament prophets fortell of Muhammad, as well (see here.)

Usually, when I read these passages, I don't pick up on anything too intensely prophetic. There are a few places like Isaiah 53 that definitely remind me of Jesus' life. However, usually, the prophetic portions of the Bible read just like the rest. If I read them with my study Bible, I see and understand how everything applies to Jesus and explains the Trinity and supports Christianity. When I read it from sources such as the first link above, I see that the Bible is obviously talking about Muhammad and Judaism and Christianity have both been twisting God's word for centuries. However, when I read them alone, I get that God is great and is worthy of our praise and that we are weak and full of faults but if I were reading the Old Testament without any other background, I don't think I'd flag any parts as prophecies.

It's also very possible that my uninsightful Bible interpretations are just a result of my own academic shortcomings. I've always been very skewed towards the maths and sciences and weaker in the liberal arts. I love reading but apparently I'm a very superficial reader, seeing only the explicitly stated and overlooking any deeper meaning.

Life (from the religious search for truth perspective) would really be so much easier if I had original, untampered sources for all the religious texts. I'm pretty accepting of the Qu'ran's veracity just because of its relative modernity and the intense tradition of memorization from the very beginnings of Islam. However, Christianity's and Judaism's texts are collections from various authors over various periods of time and their history of oral tradition provides plenty of oportunity for modification, whether intentional or not.

I'll finish by returning to a theme from my very first post. Religion is supposed to give peace. Sometimes it definitely does that. Sometimes when I'm experiencing God's wonderful creation and beauty, I'm very grateful and praising. However, whenever I remember my current confusion, religion just depresses me. I don't feel like God has abandoned me but I feel like I suddenly don't know Him anymore. I guess that's to be expected since I'm questioning my fundamental beliefs about God; I guess on some level, I don't know Him. Hopefully I'll find Him again and I'll regain that confidence and certainty of my beliefs, thereby regaining my peace and shaking this religious depression.

By the way, if you're Muslim, Happy Ramadan, if you're Jewish, Happy Rosh Hashanah, and if you're Christian, Happy mid-September!