I've had this problem for about two weeks now. It seems to do it only when the CPU is at about 135 degrees for about an hour. You might want to check how hot it's running during WoW. I think it's my logic board. Last night I went to do another Apple hardware test and it froze and the backlight turned off. I could see that the LCDs were still on but no backlight. Weird. Anyway, my MacBook has passed numerous hardware tests without a problem. It might be hardware and not just a software problem.