Just for a point of reference - I made the changes above (commenting out) and I still get the errors. I would assume this timing (Pi being used, number of devices being polled, etc.) with Ibrutti's setup that clears up the problem. I do agree that this is thread related.
I'm not entirely familiar with the python environment to understand how it accomplishes threading and what APIs are available for threading control (and don't have the time right now to delve into it!).