just my 2 cents,,,,,,,, you are correct that a power outage should not hurt the board If there were a power spike that could but with the events you described I doubt that happened so I am thinking the outage hurt the psu witch in turn hurt the board maybe on the next powerup.
It maybe impossible to track down just what is bad with the board and is it even worth it, socket A boards are relativity cheap these days, maybe the answer to future problems like these is a APC backup.
Rick