Do a clean reinstall of the current Firefox release and delete the Firefox program folder before installing a fresh copy of the current Firefox release.

• download the Firefox installer and save the file to the desktop
  *https://www.mozilla.org/en-US/firefox/all/

If possible uninstall your current Firefox version to cleanup the Windows Registry and settings in security software.

• do NOT remove "personal data" when you uninstall the current Firefox version, because this will remove all profile folders and you lose personal data like bookmarks and passwords including data in profiles created by other Firefox versions

Remove the Firefox program folder before installing that newly downloaded copy of the Firefox installer.

• (64-bit Firefox) "C:\Program Files\Mozilla Firefox\"
• (32-bit Firefox) "C:\Program Files (x86)\Mozilla Firefox\"

• it is important to delete the Firefox program folder to remove all the files and make sure there are no problems with files that were leftover after uninstalling
• http://kb.mozillazine.org/Uninstalling_Firefox

Your personal data like bookmarks is stored in the Firefox profile folder, so you won't lose personal data when you reinstall or update Firefox, but make sure NOT to remove personal data when you uninstall Firefox as that will remove all Firefox profile folders and you lose your personal data.

• https://support.mozilla.org/en-US/kb/Profiles
• https://support.mozilla.org/en-US/kb/back-and-restore-information-firefox-profiles

Reinstall Firefox

• https://support.mozilla.org/en-US/kb/troubleshoot-and-diagnose-firefox-problems

This writeup is directed to this problem on a PC. I have this problem on an iMac. Is there a Mac writeup?

Hi BudVitoff

On Mac you need to drag the Firefox installation folder to the Trash and instal a fresh Firefox version.

Download a new copy of the Firefox application and save the Disk Image file to the desktop Firefox 65.0.2:

• https://www.mozilla.org/en-US/firefox/all/

• trash the currently installed Firefox application (open the Applications folder in the Finder and drag the Firefox application to the Trash) to do a clean reinstall
• install the new version that you have downloaded
• https://support.mozilla.org/en-US/kb/Installing+Firefox+on+Mac

Your personal data like bookmarks is stored in the Firefox profile folder, so you won't lose personal data when you reinstall or update Firefox, but make sure NOT to remove personal data when you uninstall Firefox as that will remove all Firefox profile folders and you lose your personal data.

• https://support.mozilla.org/en-US/kb/back-and-restore-information-firefox-profiles
• https://support.mozilla.org/en-US/kb/export-firefox-bookmarks-to-backup-or-transfer

With all due respect, my friend, yours is not the first to suggest this solution. It was the first thing I tried even before hearing all the others and it simply did not solve the problem -- at least not for me.

Apple gave me the link to the Mozilla customer support, and with a little hunting around I did run across the Mac solution regarding this exact diagnostic message. I took a quick first look, and it involved much more than the "standard" solution, including getting into Firefox's "safe mode" and stuff like that. (I also ran across some documentation pitfalls that shows a step that was supposed remind the reader to execute it just before a couple of steps earlier, so it pays to read the entire document before you begin following it!)

I'm not going to pursue this right now, because I promised myself that I would get my taxes done first; however I will post the results of my efforts here.

Thanks for your concern.

Bud, your information was perfect for the problem. Did exactly as the URL sites suggested and the "fileFirefox can’t find the file at jar:file:///C:/Program Files/Mozilla " solved.

Thanks