I posted a thread last week concerning a new EVGA 570 that I bought. The fan on that card would not spin. It only jittered a bit. I sent it back and received a new replacement card. The fan on this card seemed to work. I turned my mac on and the fan started spinning like I'd expect. This morning I started using my mac and after a while it started acting weird. So, I shut down and popped the side off, restarted and watched the fan and it didn't spin. It only did a couple of revolutions and stopped. It repeated this until I shut down. After a few shut downs and restarts the fans started spinning again. I've tried two different power cables thinking maybe there was a short or bad connector in one of the wires. Same results with both cables. I moved the card up to slot 2 to see if that makes any difference. After installing the card in slot two the fan started spinning on the first start up. I plan to leave it there for now, but I'd be surprised if that is going to fix it. Anyway, does anyone have any clue to why this is happening? I doubt that I received two bad cards. Especially since this one seemed to be fine a week ago. Do I have enough power to run this card? I have a early 2008 mac pro. From what I read I should have plenty of power, but maybe not. Does it matter how many additional peripherals that are plugged in?