I just installed a Radeon 5770 in my Mac Pro 3,1 and didn't have 10.6.5 installed like it required, but it still turned on fine, was quiet, checked stats, RPM, temp, everything was fine for about 4 days - til today, I got the Snow Leopard disk in the mail, popped it in, went to restart, so I could install it (which, because of the driver issue, wouldn't) that's why I was installing the disk, to get 10.6.5 update. Anyway, I hold down the power button to shut it off, since it wouldn't restart -- now, it just makes a click, sometimes another click after about 5 seconds, then nothing happens. I re-plugged it into different outlets and nothing. I remember tha when i first installed the card, everytime i turned the mac on, it took about a second to actually turn on after it clicked. Is this a power supply issue? I don't get it, everything was running fine. The 5770 not running on 10.6.5 wouldn't do this, would it? I'm worried that it may be fried. Can anyone enlighten me here? It doesn't always make the click, but usually, if i re-plug it in. I also barely hear a sound like something's trying to make a connection, electrically. Ugh. Any help would be greatly appreciated. Thanks EDIT: Now, it seems to turn on fine?! all red lights blink once in unison on RAM board, as usual. All I did, was unplug the mac again, and hit power? It may seem like a hasty original post, but I'm still concerned that it could become a serious problem in the future. What can I do to make sure this doesn't happen again, or worse, permanently?