I tried deleting all cookies, completely removing Firefox and reinstalling it but it doesn't seem to work. Whatever it is has only affected Firefox. Chrome seems unaffected.
- All posts
- Helpful Solutions
Try to delete the sessionstore.js file and possible sessionstore-##.js files with a number and sessionstore.bak in the Firefox Profile Folder.
- Help > Troubleshooting Information > Profile Directory: Open Containing Folder
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).
Create a new profile as a test to check if your current profile is causing the problems.
See "Creating a profile":
If the new profile works then you can transfer some files from an existing profile to the new profile, but be careful not to copy corrupted files.