It could also be a power supply issue. I had similar problems a while back; if you by any chance have the K7S5A motherboard, then I'd say that's definitely the problem. If so, check to make sure your power supply is at least 350 watts or so. Mine was only 300 - it was a perfectly good power supply, but this motherboard is apparently very picky about what kind of juice it will drink
Search around and see if anyone else has had similar problems with your model of motherboard.
Though, if you have this problem only with a particular distro, then it seems less likely to be the problem. Though, then again, I never had problems with it under Windows - only Linux. There may be minor differences in power usage between different distros, which could be enough to nudge it towards failure. It's worth looking into! Especially if you can borrow a power supply from a friend to see if that helps. Good luck!