Hi Tom, when starting up, Firefox checks for a session history file in a specific location. If it's not there, Firefox assumes that it crashed and tries to do an automatic crash recovery using an older file.

Do you exit Firefox and allow time for it to clean up after itself before shutting down your system? If not, perhaps Windows is rushing things and Firefox is not completing its shutdown. That would cause this problem.

Another possible explanation is if Firefox is crashing during its shutdown for one reason or another. Usually the Mozilla Crash Reporter window would pop up in that case. I assume you haven't seen that?

We also warn about third party utility programs that clean browser data, such as CCleaner and Advanced SystemCare. These could trigger the problem.

Does any of that sound relevant?

Normally, I only shut down my system for a periodic cleanup. I get no reports from Crash Reporter and I try to stay away from utility programs that do not come from a trusted source such as Mozilla. None of this really applies to what is happening. As further info, I know use the home key before exiting Firefox, and have a 50/50 chance of it trying to restore or not. Color me as perplexed.