Become a MacRumors Supporter for $50/year with no ads, ability to filter front page stories, and private forums.
Wirelessly posted (iPhone: Mozilla/5.0 (iPhone; U; CPU iPhone OS 2_2 like Mac OS X; en-us) AppleWebKit/525.18.1 (KHTML, like Gecko) Version/3.1.1 Mobile/5G77 Safari/525.20)

Try rebooting your phone by holding the sleep/wake button and the home button down until you see the Apple logo. That may fix your problem.
 
A little more information would be helpful. What happens when you plug your phone in to your computer? Does iTunes recognize it at all? Does it charge at least?
 
Register on MacRumors! This sidebar will go away, and you'll see fewer ads.