Did you notice or can you check that caps on the resistor thingys (technical term) to make sure they aren't bulged or leaking gunk (another t.t.)?

If you see that they are then the MB is dying.

I'm at GreyHair's stuffing myself with curry, but I'll check when I get back home. I doubt it, it's not that old either: it's an AS-Rock M3A770DE.

Let the record show that it was a fuxxored PSU. I've stuck a new one in and it's running as right as a bobbin.