I've had my PC randomly shut down while playing FF 4 times in just over a week.Today I've been hammering GTA 4 since I couldn't play and everything has been great!! then I manage to log in at 11 only for my PC to shut down 15 minutes in. I reboot and try again and it's been fine since!!
My voltages are great on my PSU and visually there are no signs of wear,burns,bubbles ( inspected with magnifying glass ) and as I said, I can play anything else.