said by leibold:Of course, one (heat) is sometimes the cause of the other (bad data).
Quite true, but doesn't seem so in this case. 4 hours is quite a bit longer that it would need to cool. Also that it runs indefinitely (until the next power glitch) once it correctly boots, just doesn't even sound like a thermal trouble.
For trouble shooting purposes I would plug it in, unplug it and check all the caps rather quickly and see which ones were still charged, each time I found a charged cap I'd discharge it and see if it would boot normally. When I find the one that allows it to boot normally it would get a bleeder resistor.