@gregkinney,

Glad to hear you tracked the offender down.  For the other forum readers, would you mind providing a few more details on how you located/isolate the PC as the problem?  Intermittent problems are normally the worst.  It can be extremely difficult to isolate the problem to a circuit or device.

Sure @IndyMike, here's the rundown of how I fixed this issue:

I had three devices stop communicating consistently. Sometimes they would work when I tried to operate them from the admin, sometimes they wouldn't.

Two of them were on/off modules in the theater closet and had gotten inadvertently plugged into a UPS so that was an easy fix. I unplugged them from the UPS and plugged them into the wall, then went ahead and put the UPS on a Filterlinc to be safe.

The third was a 2477d dimmer switch in our home office. I ordered the Filterlinc and while I was waiting for it to arrive, I had learned that UPS's were notorious for noise. There is a UPS in our home office so I unplugged it and then plugged the PC that was plugged into the UPS straight into the wall. Still had inconsistent commuinication with the 2477d. I then unplugged everything in the room and then had consistent communication with the 2477d. After that, it was a matter of plugging things back in one at a time and testing until I found the culprit which was the PC. 

A few days later, the Filterlinc arrived and I plugged the PC into the UPS and plugged the UPS into the Filterlinc and voila! All is well now.