I'm thinking the same thing, sounds like a power issue, might need a new power supply if it happens again. also I had a motherboard that caused this once also. I'd say chances are 85% psu , 14% chance it's motherboard, 1% something else. With pc's there's always the 1% chance it's something completely unexpected lol....
crap, just noticed u said ur mother board temp was climbing passed 80c
this is too high! you need to position a fan to cool the boards bridge chip, or get more air moving thru the case!
Regardless of what any manufacture specs say, no chip should ever exceed 80c, With any chip, from any manufacturers 80c is the unwritten limit! at around 80c weird stuff starts to happen inside the chip. electrons start jumping in ways they normally would not do inside a chip, be it a CPU, a single transistor, capacitor, ect... and around 90c perminant damage starts to occur. also note, that some chips have even lower limits before damage occurs depending on complexity, and quality. but no semiconductor like 80c and up....