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)
This has happened to me a couple of times before. Here's what I did:
1) Reboot the iPhone by holding down the "Home" button and the "Sleep/Wake" button until the Apple logo appears on the screen.
2) If step 1 doesn't resolve the problem, delete an App and reinstall it.
3) If step 2 doesn't work, restore the phone.
I hope this helps. If none of that fixes the issue you may need tech support.