I also similiar problem.

Computer hangs a short while after I lauch WoW, sometimes with lines appearing all over the screen. When I reboot, these lines will sometimes persist in POST and will only disappear after I CTL-ALT-DEL for a few times. Problem will keep repeating (i.e. system hang when I launch WoW) and I find the only way out is to first load Windows in safe mode and then restart to normal. This usually solves the problem until the next day where the cycle will repeat again.

This due to Video card? I used Rivatuner to keep video constantly below 60 degrees celcius but doesnt seem to help..

I am using 4870X2.