Hi enidgh, do you get this when you want to start Firefox, or at other times after you started Firefox?

Does anything in this article help: "Firefox is already running but is not responding" error - How to fix?

Occurs when I had used Firefox and "closed" it, but during the same Windows 10 session.

Windows will close it without going to task manager, but it keeps happening and is annoying.

Hi washburns70, when you Exit/Quit Firefox, if it doesn't fully shut down within 60 seconds, a watchdog process should kill it and may display a crash reporter dialog. So this error message shouldn't appear after that 60 seconds. I guess there could be something going wrong with the shutdown process.

Have never seen the crash reporter error message. Running 64.0.2 (64) on fully updated windows 10

I keep getting messages to change your profile. I can't seem to get to my profile with the instructions. Problem is still occurring. How can I cancel the OLD FIREFOX completely?

enidgh said

I keep getting messages to change your profile.

Could you capture the message more exactly?

When Firefox is running, you can can easily view your profile list and, if it helps, switch among them. Please don't delete any profiles, since it is too easy to remove valuable data.

Profile Manager Page

Inside Firefox, type or paste about:profiles in the address bar and press Enter/Return to load it.

This page should list at least one profile and could list many. (Each profile has two folders and one or more buttons. Do not use any Remove buttons!)

The profile that Firefox is currently using will have this:

This is the profile in use and it cannot be deleted.

If you are curious what data is in another profile, you can open a new window in that profile clicking its Launch profile in new browser button.

When you close that window, the window you started with should still be there.