>>1
Yeah, do what >>3 said. Take him out to have a drink or two and just enjoy being together. Even if you're not speaking a lot. It's still better than him being locked in his room weeping on his bed. Be sure to tell him that if he wants to talk about anything you're there, but you won't ask him to. Telling him you won't pressure him into talking about his problems will reassure him.

Another way would be to share your problems with him. Be they past love problems, or current things that are bothering you, whatever. This way, you'll draw closer to his mindset (in his mind, at least) and he'll be more likely to let you help him.

I also always found soothing to be able to hear a friend's story when I was down, because it helps empathetize with his problems and diverts attention from mine. Maybe that will help.

I hope he gets better. Such things are always hard for the guy, and for the friends of this guy that feel hopeless. And feeling hopeless for a friend is something terrible. Good luck for the two of you!