Please consider turning on send info to Mozilla before posting a question. This helps us help you as it detects issues with video card, plugins and is info to work with.

If just been going along and updating and updating thinks go out of wack just like Win 7.

Suggestion have you tried turning off all extensions/plugins then a uninstall and delete all Mozilla Firefox folders in C:\Program Files and C:\Program Files(x86) (Profile is saved). Followed by a reboot, then using Microsoft Disk Cleanup empty temp files then run again and cleanup system files. Install Firefox with a Full Version Installer https://www.mozilla.org/firefox/all/ Then turn on extensions 1 at a time and restart each time and run to see if working properly before turning on the next one and a restart....

If no issues great. If issues still could be Extensions https://support.mozilla.org/en-US/kb/troubleshoot-extensions-themes-to-fix-problems?redirectlocale=en-US&redirectslug=Troubleshooting+extensions+and+themes or it could be in your profile https://support.mozilla.org/en-US/kb/profiles-where-firefox-stores-user-data and https://support.mozilla.org/en-US/kb/profile-manager-create-and-remove-firefox-profiles

And for a little Win 7 tuneup Repair System Registry and Files

(FOR DOING Above & Below - WINDOWS All OTHER VERSIONS - Use Search To Find Command Prompt ** Enter CMD.exe to Find COMMAND PROMPT Then Right Click & RUN AS ADMIN)

To run the SFC command use the Windows key + X keyboard shortcut to open the Power User menu and select Command Prompt (Admin). Type "SFC /SCANNOW" (without quotes or copy/paste) and press Enter. For more information on using SFC, please refer to the Microsoft KB: Use the System File Checker tool to repair missing or corrupted system files

Run the Windows Deployment Image Servicing and Management (DISM) and System File Checker (SFC) tools as Administrator. The DISM and SFC tools scan the integrity of the Windows image and all protected system files replaces corrupted, damaged and incorrect versions. (FOR DOING Above & Below - WINDOWS All OTHER VERSIONS - Use Search To Find Command Prompt ** Enter CMD.exe to Find COMMAND PROMPT Then Right Click & RUN AS ADMIN) Type "DISM /Online /Cleanup-Image /RestoreHealth" (without quotes or copy/paste) and press Enter. Note : SFC fixes files locally using files found on your system. Note : DISM goes up to Microsoft for new ones. Oh ya do not forget to run chkdsk command with switches http://www.thewindowsclub.com/command-line-check-disk-windows-7

Note : Firefox 57 Quantum release date Nov 14th https://www.mozilla.org/en-US/firefox/quantum/ Note : Legacy Extensions will be disabled and or removed.

Please let us know if this solved your issue or if need further assistance.

Is that the only personal data you lose?

The exceptions are part of the Site Preferences and are stored in content-prefs.sqlite. If you lose the exceptions then the Site Preferences might be cleared somehow or there might be a problem with the content-prefs.sqlite file.

You can use the button on the "Help -> Troubleshooting Information" (about:support) page to go to the current Firefox profile folder or use the about:profiles page.

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