Simple.. You need to go back to the latest iOS6 update.. iOS 6.4 i think it is

You must login or register to view this content.

Looks like Apple is finally blocking users out of iOS 7 who do not have their iDevices UDID activated

So you have to go back to iOS6...

#1 Download the latest iOS 6 IPSW for your iDeivce here You must login or register to view this content.
#2 Once the IPSW is downloaded go into iTunes ( Make sure you have backed up your iDevice )
#3 Go to your iDevices Tab and Hold SHIFT + TAB and click on Restore iDevice
#4 Find the IPSW you D/Led, It will wipe youe iDevice and install iOS 6
#5 Sync your iDevice once its finished you will have everything back to normal ^^