Of a similar failure I had on a dual Pentium Pro system I had long ago. This can be repaired. Go get the usual HDD power Y cable and use that to solder in just the wires and connection you need. This took me about 20 to 30 minutes and the machine lived on for many years.
The cause was/is simple. There a lot of power flowing though and the electron flow can weld the connections together over time.
The other day my pc wouldn't power on, and after diagnosing all external power related problems, I grabbed my psu tester and found one of the 4 pin connections to my motherboard has snapped off when I unplugged it.
I have previously replaced the psu a few years ago, but other than that, I haven't touched that connection point, so it is possible that I damaged it during the replacement.
The voltages all read ok from the psu, so my question is: Should I risk buying a new mobo when there is potential for the cpu to be dead? - I've never encounterd a dead cpu so don't know if the mobo will attempt to power on if it is.
The board is a Asrock Z68 Extreme4 Gen3


Chowhound
Comic Vine
GameFAQs
GameSpot
Giant Bomb
TechRepublic