Quote Originally Posted by MadBeaver
I had a similar problem a few years back. The pc would just shut down when ever it felt like it. I replaced the power supply, with out any change. In the end it was the motherboard.

Good luck
I'm currently having that problem. It doesn't restart like the OP's does. It just shuts down. Nothing in the logs. No messages about there being an error after I reboot. It acts perfectly normal. The only times it happens is when I'm playing a graphically intense game or trying to encode avi's to DVD. At first I thought it was a power problem, since I was using a weak supply (350W), but after exchanging that for a 550W it still happens.

Looks like I'll have to pony up the dough for a new MB. I need one anyways, since my current is limited to 4GB RAM.