i have this problem where my iMac will randomly shut off. I mean just complete loss off power as if the plug was pulled from the wall. I had it in to the Genius and they said it was the RAM. They replaced that and I get it back and it still has issues. I am thinking it is the power supply. Anyone else have this issue? Is there anything I can check before I take it back in? I checked the logs and it just notes a power failure.