hello creosote1, please press the windows-key+r and open:

firefox.exe -p

then a profile manager should show up - in there select to create a second profile and try to launch firefox with the new one.

Profile Manager - Create, remove or switch Firefox profiles

Profile Manager does not open, get crash report window again, latest report: Crash ID: bp-b7453d29-35fc-4c7d-ae1c-2511d2141003

does it make a difference, when you press the windows-key+r and open:

%appdata%\Mozilla\Firefox

in this folder rename the file profiles.ini to something like oldprofiles.ini and try to start the browser again...?

Afraid not no, a new .ini file was created but still get the crash reporter.

ok, if ithat step didn't help then please revert that change (delete the newly created .ini and rename the oldprofiles.ini back to profiles.ini).

another thing that i'd try in this situation is a clean reinstall:

1. please try to uninstall firefox from the system control panel.
2. then go to the firefox program folder (usually located at C:\Program Files (x86)\Mozilla Firefox) and delete any remains of the firefox program folder after the uninstall manually
3. afterwards reinstall the browser with a fresh copy from https://www.mozilla.org/firefox/all/

That seems to have worked, anything else I should be doing?