I just picked up my iPad yesterday, 16 GB WiFi model, and I'm having a problem... I'll be using the iPad for a while (maybe 30 to 45 min), when suddenly the screen shuts off. I can still somewhat see, but it is very very very dark. The sound continues fine and it still recognizes my finger inputs. The only way to get the display back is to reset the device. Is this some sort of hardware issue? Should I take it in and have it replaced?