@DarkKing - injury and disease (because disabilities ARE diseases, only differing from what most people consider disease in that they are caused by our own bodies stuffing up (mutations in DNA) rather than pathogens) are not sins themselves, nor are they a direct cause of sin (by direct I mean you sinned therefore you will get a disease). Diseases are a result of God's curse of the Earth, which was a punishment for our sin. Because of our sin, the world is no longer "good" and therefore we have diseases. Does that make sense?
Natural causes of disability are not mentioned, it is attributed to God.
natural causes of those diseases aren't mention, because they weren't known when the Bible was being written!
It's not like the Bible authors deliberately ignored the natural causes in order to push their religious propaganda, as your statement seems to me to imply.
God brings disability as punishment for transgressions for sin or as an expression of God's wrath for people's disobedience.
This was (is?) indeed the Jewish belief, hence the disciples' question. While we have to be clear that Jewish beliefs definitely don't necessarily equate to Jewish beliefs, this statement is not altogether wrong, though not precisely true in the Christian faith.
As I mentioned before, disease is a result of God's curse on the world, which was a punishment for human sin. So, there is a link between sin and disability, though it's not quite the I-killed-someone-therefore-I'm-going-to-get-leprosy type link.
That's why it's kind of interesting that Jesus not only healed people of their physical sickness, he also forgives sins - the ultimate cause of our suffering. Only God could forgive sins, which is why saying "your sins are forgiven" is as good as saying "I am God".
"See, you are well again. Stop sinning or something worse will happen to you" (Jn. 5:14)
I found this quite interesting, I'd never really noticed the second part of this verse before. However, when it says "Sin no more, lest a worse thing come upon you." (NKJV), my guess (guess, mind you, I'm not a Bible scholar) is that this second part is not referring to a physical sickness; something a lot worse than physical sickness, imo, would be spiritual death (eternity in hell). I think that is perhaps what Jesus was referring to, but again, that is just me, and not necessarily an accepted theological truth of Christianity.