Hi Alan,
I get this issue from time to time. I got it several times, if I was running win update or other grafik related software updates while ANRB software was running. Either ANRB SW crashes during the update or the stated problem with remaining flights happens. But it seems depending on what kind of fix is installed. On some rare occasions I got this after a teamviewer remote session too.
Both of my PCs on which I'm running ANRB SW (24/7) are running WIN7 64bit, but I'm only getting this on the stronger machine. Until now I wasn't able to find an explicit mechanism to force it to happen. This is an issue that will be very hard to fix as now "force-point" was discovered yet. From my own programming experience I'll fear that this one might only be fixed coincidentally by fixing some other issue.
Regards Ingo