It sounds to me like your power supply is on the way out. That could have been caused by a spike when the ups fried. Not very technical terms, I know, but descriptive. A new power supply is not that expensive or try swapping one out from an old computer. I have a graveyard in the basement for problems just like this. I can't tell you how many times I have said - gee, I've never seen that happen before. I hoard old but still working parts and then I can replace stuff and solve problems by process of elimination.

Kathleen