I had a similar issue years ago when I lived in a crappy apartment with bad electrical wiring. I lost 3 boxen while living there. I eventually went ahead and grabbed an APC surge protector and I had no further issues. I agree with SirDice, this sounds very much like a power surge/sag issue. How old is that UPS you have? Good quality brand or CompUSA special? I have seen cases where the UPS becomes FUBARed and throws out huge power spikes.

--TH13