What should you do if your boyfriend won't talk to you?

I'd ignore him! Don't give him the benefit of the doubt. I know it hurts and you probably don't even know why he's acting this way. It could be another girl he is seeing or he's just a plain jerk. Get on with your life. Go out with friends and before you know it you'll find a nice guy that will treat you much better.

If you truly don't know why he is behaving that way, like the above suggests, then its simply time to move on.

You probably DO know why he won't talk to you. You can either apologize, (wether appropriate or not, this will get him talking) so you can have a mature discussion about the matter, or you can learn from the mistake (whos ever it was) and move on.