Hello Paul,

That's a very odd behavior indeed. All I can think of is that an add-on is confused and makes Firefox crash. The Reset Firefox feature can fix many issues by restoring Firefox to its factory default state while saving your essential information. Note: This will cause you to lose any Extensions, Open websites, and some Preferences.

To Reset Firefox do the following:

1. Go to Firefox > Help > Troubleshooting Information.
2. Click the "Reset Firefox" button.
3. Firefox will close and reset. After Firefox is done, it will show a window with the information that is imported. Click Finish.
4. Firefox will open with all factory defaults applied.

Further information can be found in the Refresh Firefox - reset add-ons and settings article.

Did this fix your problems? Please report back to us!

Thank you.

I probably wasn´t clear enough in my description, but Firefox does not crash. It stays open throughout. Firefox, for some unknown reason, appears to be causing Windows Explorer to crash when opening a private browsing session from the pinned Firefox icon on the task bar. No other application in my computer has ever caused such a crash to Windows Explorer as far as I can remember. Oddly enough it does not happen in 100% of the cases, so there are other factors probably playing a role in this behaviour, but I have not managed to identify them yet. FireFox actually often crashes when I have multiple tabs open and click the "X" to close all windows. I´ll rty the reset anyway. Thanks for the advise.

Not sure if it helps, but print screen is attached.

Boot the computer in Windows Safe mode with network support (press F8 on the boot screen) as a test to see if that helps in case other software that is running is involved.