Chris:
When you wrote the reply just now wee you looking at the schematic? Or did you do as I suggested and check each pin while the program was running. It is a very common problem that we believe that our circuit is perfect only to later find that we had an accidental short or we had wired something different from what we had on the schematic. I really suggest that you need to watch every processor pin with an oscilloscope while the program runs. Alternatively you could use an ohm meter to test for short from every micro pin to any node of the circuit that has possibility of voltages over VCC or below GND. If you use the ohmmeter technique do it while the power is off.

Michael Karas