Most likely a problem to do with your firmware or OS. Try making a backup and then restoring to that backup. If that still doesn't work then restore it without any backup. But make sure you back up your contacts with Gmail or some other service that apple offers in iTunes.

I got the same problem

I found out that the problem was occured by connector 3 of the screen.

After i replaced the screen it worked back like it should be =D

My phone is also the 1st Generation. But I hav a diff problem. My iphone just cant charge!I've tried to unplug it & then plug it into my ipad (just to make sure it was the phone's fault & not the charger's).Like i thought,it was'nt the charger's fault!I've tried charging it from the docking device, the ipad charger & NONE works!!! I'm really desperate now!!!! ANY ADVICE???????????

stick your 1st gen in a wall charger if you can get it to the home screen

hold down power then swipe off then leave overnight. Then hold down power and home untill apple logo apeers that should of charged it if not try sticking it in dfu mode in your wall charger over night then try what ive allready said it works for me but your battery could be nackered probly a software issue like mine though.