You can check the target line in the Firefox desktop shortcut (right-click: Properties) to make sure that nothing is appended after the path to the Firefox program.

You can check for problems with preferences.

Delete possible user.js and numbered prefs-##.js files and rename (or delete) the prefs.js file to reset all prefs to the default value including prefs set via user.js and prefs that are no longer supported in the current Firefox release.

• http://kb.mozillazine.org/Preferences_not_saved
• http://kb.mozillazine.org/Resetting_preferences

You can check for problems with the sessionstore.js and sessionstore.bak files in the Firefox profile folder that store session data.

• Help > Troubleshooting Information > Profile Directory: Show Folder (Linux: Open Directory; Mac: Show in Finder)
• http://kb.mozillazine.org/Profile_folder_-_Firefox
• http://kb.mozillazine.org/Multiple_profile_files_created

Deleting sessionstore.js will cause App Tabs and Tab Groups and open and closed (undo) tabs to get lost and you will have to recreate them (make a note or bookmark them if possible).

To the extent that I could, I tried the above, despite the lack of clarity at times. For example, how do the uninitiated find "sessionstore.js" and "sessionstore.bak" and the Firefox profile folder? Assuming that I eventually find them, what in the world does "check for problems" mean?

There are many of us out here with limited to moderate computer sophistication, and more detailed suggestions would be much appreciated. I am in the moderate to high category, but much of your response was marginally useful, to be kind. Not to say that I don't appreciate what you have written.

hello, could you go to the firefox menu ≡ > help ? > troubleshooting information, copy the contents of that page and paste them here into a reply on the forum? this might give us a clue what is going on...