My Iphone 4 will not connect to my computer and itunes?

I have done it before. I have connected it to my computer, and put songs onto my phone through itunes. But now for some reason, it won't connect to my computer, and it won't open in itunes. This is really starting to tick me off. What can i do?

Added (1). I connected to my computer last time, and it connected fine and connected to itunes. Now with the same cable, it will just start charging when i connect in to my computer but it will not connect to itunes. I have tried different cables but that doesn't seem to work either. I don't know what's going on here.

Maybe your cable, or whatever you use to connect your phone, is broken? I dunno. You need to give more information.