Yup... Sounds like the power cut killed the PSU... It happens. With the ATX standard, the PSU is never truly OFF (as in isolated from the mains supply). It stays in standby talking to the mobo on the +5VSB (I think), waiting for the mobo to report that the button on the front panel has been pressed. At that point it fires up and supplies power down all it's rails.
This means that a sudden spike, of the sort that goes on the mains supply either immediately before or, more likely as the power comes back on can pop an ATX PSU.
I always buy PSUs with a hard switch on the rear... (Two of my machines are protected behind UPSes) When the power goes down, I isolate the PSu form the mains with this hard switch and only re-apply power once the mains voltage has stabilised. (About 5-10 minutes after the power comes back on in the worst case scenario.) That way, the supply doesn't get hit by the spike when mains power is restored.
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