How can I synch my iTunes? If often says unknown error or problem with application?

I have problems synching my iPhones 4s with my MAcbook pro (10.8.2) and iTunes (11.0.1). I can connect my iphone 4s(6.0.1) directly to my macbook pro or via the same network. I can start the synch via itunes or my phone. 20% of the time it works. If often says unknown error or problem with application. The software is up to date. What can I try? Thank you