Or, it could be a motherboard error. ATX power-supply's are switched on and off through the motherboard, and if something was screwed up, it might not turn on the power-supply. First of all, make sure that your ram is in properly, and nothing is loose on your motherboard. You could have a lose connector, and when your computer tries to access a certain bit of memory, it cannot and crashes. Also after it crashed, have you tried simply unplugging the computer for like 5 mins? That would make sure all capacitors are drained, and all memory is emptied.
I have seen all sorts of problems with motherboards not doing what they are supposed to - they are the largest component in your computer, and there are so many things that can go wrong. Also, could you post a list of your computer spec's? If you need it here is a copy of
EVEREST Home edition. Everest will give you all the info you need(and lots more you dont!).
Of course, it could simply be your power-supply overloading, but it would probly start up again in 5 mins or less if that was your problem.
-Robbie