Of course, reality has just altered itself to work against me. As is often the case.
For the past 2 days I have been able to generate this error at will. As soon as I set up a debug environment to capture data for you - the error goes away. Now, even if I enable "All Stores", I no longer receive the error.
However - I do have a log file that I captured yesterday that I can send to you. When I was still getting the error. I will send this to you and hope that it can shed some light on this problem.