It sounds like you believe that this is not an ISY (hardware or software) problem, and I accept that conclusion. I just wanted to be sure. My problems beginning so close to a software upgrade had me wondering.
I assume that your reference to "device" having a corrupted database is to the plug-in module. I have removed from the ISY several times and performed a factory reset. I will try again, believing that this is what you are suggesting.
The device (assuming, again, that you are refering to the plug-in module) is attached to two lamps, incadescent. There is also an X-10 module plugged into the pass-through outlet (the X-10 module works flawlessly). The second (of two stubborn) devices is driving one lamp, incadescent.
While it has been a while, I think I have also tried moving the modules-in-question closer to the ISY. I think this eliminated the problems, making me think my basic noise, but I will try that again to confirm. If I can only identify the source of the noise. My house is full of TVs, computers, appliances, wall warts, CFL bulbs. The frustrating part is that this was also the case several months ago when things were working well and I think I have eliminated anything added over tha period. I will keep thinking and trying.
Thank you for your feedback.