Why does someone hate me for no apparent reason?

I have 2 people who hate me for absolutely no reason. They never look me in the eye. One of them avoids me at all costs. The other one becomes really angry when we talk. I was friends with both at the beginning of the year(not very good ones, but acquaintances), but all of a sudden it went bad. In the first case, we used to sit next to each other in cl, but one day when i sat in my desk he abruptly and rudely moved away without a word and left me utterly confused. The other person i approached and tried to start a conversation with, but he called me a moron and left for no apparent reason. Oddly, these two seem to be the only people who hate or dislike me, but it always bothers me why they do hate me. What are some possible reasons for this? And how can i deal with these people when i see them; I can barely look them in the eye without feeling oddly guilty that i let them down in some way.