Here's the schematic if you don't already have it.
http://www.usfirst.org/uploadedFiles...0schematic.pdf
Apply power to the board and (Disconnect the outputs that go to the RC just in case) check pin 2 on J2 for 5V with a meter. If it's not there, the 5V regulator is the most likely failure.
If you're still not sure, then desolder pin 1 of the regulator, apply power and see if there is 5V on pin 1 of the regulator. This will eliminate a possible short on the board as the problem. If there's something other than the regulator I suggest trying to get a replacement from FIRST. They will probably have spares at the regional.
Good luck.