Well I had the same problem and have found multiple solutions. 1) reboot/hard reset the phone by holding down the power and home buttons. Worked for me. Put the phone in dfu (device firmware upgrade(google how to...)). A restore in iTunes actually does not totally wipe the phone. Most people are surprised when they hear this but when you click upgrade or restore it does not wipe the phone. It replaces system files. By placing the phone in dfu mode, it will be wiped. You can then restore from a back up or set it up as a new phone. This wipes the cache(s) in the phone which is, I believe, the problem. Another method is to jailbreak, ssh into it and delete the cache but that's more work and that won't make apple happy so I will discourage that option on this board. Just look up how to put iPhone into dfu mode. Be exact with your timing. It may take many tries; be patient! Good luck. Always try a reboot/hard reset first though. Worked for me.