iphone won't sync with itunes

hi, ive got an iphone which has been working fine unitl now. nothing seems to sync anymore, itunes recognises the phone, but everytime i try to sync it says that its syncing for a few seconds, but then it stops and nothing has been synced. so now none of my musc, apps or videos gets synced. can anyone help? thanks

have you tried restoring the phone? that might help.

**however, if you have a jailbroken iphone that's another story.