Unless you've got an anti-aircraft searchlight plugged into the Zorro bus, there isn't enough power consumed by the motherboard to burn connectors. I would suggest that your problem is worn/bent connector pins. If you have a close look at the female "pins" on the mobo, have they been opened out by frequent plugging/unplugging? (No ribald comments, please). You could squeeze them together again with a small pair of pliers or tweezers (very gently, of course). Just enough so that the plug sits firmly in the socket when you replace it. The edges of the hole in the "pin" should just meet.
[edit - better explain that a bit better] The "pin" is of course a socket for the pin in the PSU cable's plug. The "pin" on the mobo should be a small circle, with no gap where the two "ends" of the circle meet. If there is a gap, the contact will be loose.[/edit]
While you're at it, check that the cables are not damaged and hanging by only a few strands. That could also cause overheating. So could a "dry" solder joint on one or more of the mobo pins. If they are loose in the mobo connector, the board will have to come out and the pins resoldered.
tony
