hello dabele, this seems to be fairly prolific startup crash at the moment. other affected users have reported that it's solvable through a clean reinstall, but developers are still seeking to investigate it further. would you be willing to help in troubleshoot?

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 pack-up the contents that remain after an uninstall into a .zip file that you can upload to a filehoster and share with us.
3. delete the whole firefox program folder manually afterwards and try reinstalling the browser with a fresh copy from https://www.mozilla.org/firefox/all/

thank you

This solved my problem.

I did zip the contents of the "Mozilla Firefox" folder after the uninstall. But I am not sure if I can provide it to you. (Since I am at my place of work, I am not sure if I am allowed to send that information to you.)

could you check with your it department or employer if they'd give you permission to do that (in general the firefox program folder does not hold sensitive data, this would be stored in your user profile)? if it's not ok to put it on a public filehoster, then maybe we can relay a mail address of a mozilla employee working on it which will treat this information confidentially.

as background on this issue: it's currently a top startup crasher and investigated in bug #1063052

I did get approval to send the zip file. How do you want me to get it to you?

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