After getting rebooted, I did try the 'crashfirefox.exe' when Firefox was running, and it did indeed force a crash, so the executable is OK.

I finally tried a Restart from the Start menu, but that process hung up on 'Logging Out' so I still had to hit the hard-reset button on the big box. Then I ran 'crashfirefox.exe' and it opened a CMD window, searched for the firefox task, and stopped dead. Of all the times for Firefox to crash, it was when I was trying to select the destination file for 'crashfirefox.exe'! So I opened (boo, hiss) IE and used it to download the file. In fact, brand-new updates were installed yesterday and today, so I don't know yet if the problem is solved by the updates I have been keeping the computer and Firefox totally up to date. I'm a tiny bit suspicious of keeping a Facebook tab open all the time, but haven't investigated that thoroughly. Removed AdBlockPlus and replaced it with uBlock Origin Ran the Extended memory check with perfect results Used my installed Norton anti-virus to do a full scan of the computer (not the online 'extreme' anti-virus) Troubleshooting that I've tried so far without success: What's really weird is that even when Firefox is frozen, other programs like Thunderbird are still working and happy. At that point, the only thing I can do to recover is to hit the hardware force-reset button.

If I try to force Firefox to shut down by opening the Task Manger, typing CTRL-ALT-DEL, the entire computer screen goes black.

The cursor becomes an hourglass within the Firefox window, although it's an arrow when pointed to the 'close' X. That is, the Firefox screen freezes (and sometimes it says 'not responding'). Sometimes, when opening a new tab and then going immediately to a search bar entry, Firefox totally crashes. All of a sudden, within the last two weeks, it's started having problems. I've been using Firefox on this computer for years with no problem.

Firefox flash plugin crash no report