My "friend" is ignoring me.

[Gaijin]

In some cases, it's not what you done, but more what you haven't done.
Since he doesn't speak about his Problems, he might want you to recognize that he has something on his mind, and ask him about it.
I was your friend once, I got really mad at my best friend because we started smoking weed, and that was all he could think of, smoke weed and think about what to do, instead of doing something.
Anyway, I was mad at him because he didn't notice that I didn't want to get high and just sit around like I'm waiting to die. He also refused to listen to me about that, because of my aggressive stand, so your friend may be angry because he can't see you as a friend or he may have changed and consider you wrong type of Person for him to be seen with or to hang out with.

I would say, you should remind him of your friendship and show him that you 2 can have fun together.
Friendship with any person is like a relationship between Man and Woman, just without the desire to have sex with the person, lol.
Ask him if there is anything you did, if the answers is "No!", ask him why hes acting so. If you really want to know what's up, you need to ask the right question, if needed even force him to answer.... In the end, you 2 will either continue to hang out, or simply go each on his own way....

Friends come and go man, even best-friends, even childhood friends....