nasty:
Are you able to verify the psu output voltages with a meter, or slave in a spare psu ? I would also suspect the psu, as those things are full of feedback protection loops. The failure of the fan could well have triggered something else that hasn't reset. Without the psu diagrams you are flummoxed, so again, a spare psu would be an easy test option :-D
Edit: Oh you have already tried 2 psu :-?
