Hi guys. I'm new here. Need help. A few days ago my Mac Pro randomly turned off. I was able to turn it back on, but it wouldn't start up (the power light comes on, but nothing else seems to happen). I stared blankly at my computer, with the power on and nothing else happening. About half an hour later, suddenly the "Apple chime" sound hit, and it started up! Maybe 15 minutes later (give or take) it shut off, and once again it would turn on, but wouldn't start up. I left it off overnight. Next day, it turned on and started up. With OSX running, I made sure to check the hard drive using Disk Utility to verify the disk. No problems. But after running it for 1.5-2 hours it shut off again. Same thing -- it turned on, but wouldn't start up. Just turned it on now. It turns on and starts up. Verified the disk again (OK). But I don't want to risk making the problem worse, if it should randomly shut down again. It's an Intel Mac Pro, 8 Core, running OSX 10.6. Bought it used, and I think it's a 2007 or 2008 model.