It's possible that maybe the Firefox update did not complete properly. You can try reinstalling Firefox and see if that helps.

It is possible that your firewall or other security software blocks or restricts Firefox without informing you, possibly after detecting changes (update) to the Firefox application.

Remove all rules for Firefox from the permissions list in the firewall and let your firewall ask again for permission to get full, unrestricted, access for Firefox and the plugin-container process and the updater process.

See:

• https://support.mozilla.org/en-US/kb/server-not-found-connection-problem
• https://support.mozilla.org/en-US/kb/Firewalls
• https://support.mozilla.org/en-US/kb/fix-problems-connecting-websites-after-updating

Thanks for the replies. Unfortunately, neither reinstalling or changing firewall rules helped.

I tried to simplify the problem I have been having when I posted here, and maybe I left out too much of it.

I have been having problems for a while where one version of Firefox would run fine, but the next one would fail to launch. That is, version X would work, but version X+1 would not. Upgrading to version x+2 would usually fix the problem. This happened for six versions, and the pattern only recently stopped. Firefox version 78.0 started fine, while 78.0.1 would not launch. Upgrading to 78.0.2 did not help.

I didn't think to record all the previous versions, but in the pattern of the current versions makes me wonder if the problem could have to do with the issue of full releases versus point releases. This seems unlikely, but stranger things have happened.

Does this help anyone see a possible solution?

While searching for other support issues that might be similar to mine, I found one that mentioned the "Windows Event Viewer". I tried to launch FireFox again, and then checked the Event Viewer.

There is an entry for firefox failing, but the information it gibes doesn't help me much. Maybe someone else knows what it means. The log messages are:

Faulting application name: firefox.exe, version: 78.0.2.7494, time stamp: 0x5f060be6 Faulting module name: firefox.exe, version: 78.0.2.7494, time stamp: 0x5f060be6 Exception code: 0xc0000005 Fault offset: 0x0000000000012863 Faulting process id: 0x1428 Faulting application start time: 0x01d65f8957aeff60 Faulting application path: C:\Program Files\Mozilla Firefox\firefox.exe Faulting module path: C:\Program Files\Mozilla Firefox\firefox.exe Report Id: 95636236-cb7c-11ea-9312-b0104177e930

Does anyone see anything in this that helps identify the problem?

While searching for other support issues that might be similar to mine, I found one that mentioned the "Windows Event Viewer". I tried to launch FireFox again, and then checked the Event Viewer.

There is an entry for firefox failing, but the information it gibes doesn't help me much. Maybe someone else knows what it means. The log messages are:

Faulting application name: firefox.exe, version: 78.0.2.7494, time stamp: 0x5f060be6 Faulting module name: firefox.exe, version: 78.0.2.7494, time stamp: 0x5f060be6 Exception code: 0xc0000005 Fault offset: 0x0000000000012863 Faulting process id: 0x1428 Faulting application start time: 0x01d65f8957aeff60 Faulting application path: C:\Program Files\Mozilla Firefox\firefox.exe Faulting module path: C:\Program Files\Mozilla Firefox\firefox.exe Report Id: 95636236-cb7c-11ea-9312-b0104177e930

Does anyone see anything in this that helps identify the problem?

If you want to reinstall Firefox, follow the instructions below. If you just want to remove it, disregard the install instructions.

Let’s do a full clean re-install;

Note: Firefox comes in three or more folders on all computers. They are;

Maintenance: (Programs Folder) <Windows Only> Firefox itself: (Programs Folder) And two folders in the profile of each user on the computer for each Firefox profile for that user.

If you remove the Firefox folder, the user profiles would not be affected.

Download Firefox For All languages And Systems {web link}

Save the file. Then Close Firefox.

Using your file browser, open the Programs Folder on your computer.

Windows: C:\Program Files C:\Program Files (x86) Note: Check Both Folders

Mac: Open the "Applications" folder. https://support.mozilla.org/en-US/kb/how-download-and-install-firefox-mac

Linux: Check your user manual. If you installed Firefox with the distro-based package manager, you should use the same way to uninstall it. See Install Firefox on Linux; https://support.mozilla.org/en-US/kb/install-firefox-linux

If you downloaded and installed the binary package from the Firefox download page, simply remove the folder Firefox in your home directory. http://www.mozilla.org/firefox#desktop ++++++++++++++++++++++++++++ Look for, and remove any Mozilla or Firefox program folders. Do not remove the Mozilla Thunderbird folder if there is one.

Do Not remove any profile folders.

After rebooting the computer, run a registry scanner if you have one. Then run the installer. +++++++++++++++++++++++++++ If there is a problem, start your Computer in safe mode and try again.

http://encyclopedia2.thefreedictionary.com/Linux+Safe+Mode This shows how to Start all Computers in Safe Mode; Free Online Encyclopedia