I still can't figure it out. I don't think it was the actual temperature, there must have been something that was going haywire to make it think it was getting that hot. Like I said, I physically touched it and it wasn't at all hot, all fans (including CPU fan) were running fine. It's an absolute mystery.

I've been sitting here for over an hour WATCHING it and it's still MAINTAINING a decent temperature well below 50. He's pleased all is working. I asked him if he still wanted me to change out the motherboard just in case and he said no, as long as it was working now to just leave it be and he'd pick it up tomorrow.

I am gonna put a BIT of stress on it for a bit and see if it maintains its cool. Think I'll install Mass Effect or something equally demanding and see how it fairs then.An hour of Mass Effect on maximum settings, temperature reached 53C max and all was smooth. Returned to 38C about a minute or so after exiting.How odd . . . I really don't see how that happened.
Must have just been a glitch, there's no way even with BADLY applied/bad thermal paste and the STOCK cooler that the temperature could jump that high that fast under no load.
Glad to hear you got it sorted anyway.Removing it and re-seating it actually may have done the trick when you re-applied the Thermal Compound...
I had this happen to me twice the last 5 years. One unit i removed and reseated the heatsink/fan combo probably 5 times before it worked normally...