I ordered the EXACT same power supply (as far as I can tell) from
us-depot for about $30 after shipping.
Since the old supply is dead anyway I'm going to isolate that one regulator that was grounded to the heat sink. Maybe that was the cause. But, first I'm going to do some measurements on the aluminum heatsinks and see what kind of voltage they have on them before I alter ANYTHING.
Also, I really do suspect I got sloppy and left a very small sliver of solder on the board. I'm going to double check EVERYTHING this time around.