I have an early 2011 MBP. It is running Lion (shipped with it) and I got it in August. Extra careful with it, it's my baby, no drops or anything. Lately, sometimes while using the computer on battery power while in my bed or sitting on the floor, if I move the computer the screen will go to black. If I push the power button, everything pops back like normal except I'm at the log in screen. Does anyone know what could be causing this?