It actually hangs up on re-execution. I cannot get into FF to change any settings.

Try to delete the sessionstore.js [2] file and possible sessionstore-##.js [3] files with a number and sessionstore.bak in the Firefox Profile Folder.

• Help > Troubleshooting Information > Profile Directory: Open Containing Folder
• http://kb.mozillazine.org/Profile_folder_-_Firefox

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

See also:

• [1] http://kb.mozillazine.org/Session_Restore
• [2] http://kb.mozillazine.org/sessionstore.js
• [3] http://kb.mozillazine.org/Multiple_profile_files_created

See also:

• http://kb.mozillazine.org/Firefox_crashes
• https://support.mozilla.org/kb/Firefox+crashes

I dinked around and:

1. renamed sessionstore.js to !sessionstore.js (I found this file from its date/time stamp)

2. I restarted FF but apparently lost my group tabs. so I

3. deleted the newly created sessionstore.js &

4 renamed !sessionstore.js back to sessionstore.js &

I am back & running with my old group tabs.

The path to the file (on my computer) was:

C:\Users\Gerry\AppData\Roaming\Mozilla\Firefox\Profiles\cv5sgp0h.default\sessionstore.js

I (and the community) would probably like a simpler process if one exists.