unable to connect iphone 4 with itunes

Hi there!

For two months now i'm unable to connect my iphone 4 with itunes. I've tried everything said at the support page of apple but nothing helped.

First i didn't mind, but now i'd really like to synchronize my iphone for some new music and updating apps..so please help me.

Rebooted iphone 4

Re-installes itunes

tried to fix it with msconfig - didn't work

But i just don't want to reset my iphone because i don't want to loose all my data.

Thanks