Question

1. We all use the same condenser/compressor
2. My office is the only one not working and blowing hot air now
3. This unit seemed to work the first day I got to office, then stopped.
4. numerous a/c people came to check the thermostat and could not fix it
5. leads me to believe it's a bad circuit board or something in the unit

Answer 1

That is certainly a possibility but there could be other reasons. Without being able to properly diagnose it, we would recommend going to http://www.mitsubishicomfort.com/ to locate a Mitsubishi Diamond Dealer in your area.