» Thu May 17, 2012 12:20 pm
Two questions:
1) What are your CPU/GPU temps when this happens? (You can use a program like Core Temp to monitor and log this. It will log temps until the moment of shutdown, and hopefully save that log so you can look at what was going on once you get the PC rebooted.)
2) Does your computer power off and stay off, or does it power off and then restart immediately?
I had a very similar problem a few months ago, although it was harder to diagnose--happened much more intermittently. In my case, my PC was powering off and then restarting immediately. Turned out the PSU had gone faulty.
The first thing I'd suspect in your case is that your PSU has gone bad, but I wouldn't rule out overheating, either. If your PC is powering off and staying off, that often points more to overheating than PSU failure.