I have now done an exhaustive search of the AFLT code. AFLT does not explicitly raise this error message. Yet you are getting it and I have once (that I recall). So, somehow, AFLT is issuing the message. The text of the message is reporting an exception condition, but the form of the message indicates it is a managed exception (i.e. one that AFLT handles to some extent). There ore only two places in the AFLT code where this message could originate, i.e., importing data (which you didn't mention) and when AFLT attempts to determine if Flightsim is running. I'm guessing it is somehow related to the latter.
I have tried numerous times, with various data, to force the error. So far, no luck. If you (or any one else) know a way to reliably force the error, please zip up your entire AFLT folder and, as best you can, tell me how to do it.
In the meantime, I'll keep trying.
Don