hello Eamon123, maybe the database that stores this information got corrupted somehow.

please go to firefox > help > troubleshooting information > profile - show folder & close firefox. in the windows that opened up look for the file named content-prefs.sqlite and delete or rename it. the database will be regenerated the next time you launch firefox & hopefully the custom zoom levels will be stored again in the future.

madperson: I did that and the language is still being reset.

You can check for problems with preferences and try to rename or delete the prefs.js file and possible numbered prefs-##.js files and a possible user.js file to reset all prefs to the default values.

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

Start Firefox in Safe Mode to check if one of the extensions (Firefox/Tools > Add-ons > Extensions) or if hardware acceleration is causing the problem (switch to the DEFAULT theme: Firefox/Tools > Add-ons > Appearance).

• Do not click the Reset button on the Safe mode start window or otherwise make changes.

• https://support.mozilla.org/kb/Safe+Mode
• https://support.mozilla.org/kb/Troubleshooting+extensions+and+themes

You can consider to reset Firefox.

• https://support.mozilla.org/kb/reset-firefox-easily-fix-most-problems

If you reset Firefox then a new profile is created and some of your data (bookmarks, passwords, cookies, form data) is automatically imported and your current profile will be moved to the desktop (Old Firefox Data).

You can recover more data from the old profile (be cautious with doing that).

• https://support.mozilla.org/kb/Recovering+important+data+from+an+old+profile

co-rel: I reset Firefox and the language is still being reset.

What is the value of the spellchecker.dictionary pref(s) on the about:config page?

• http://kb.mozillazine.org/about:config

Do you have a user.js file in the chrome folder in the Firefox Profile Folder that may be overriding the current setting on each start of fx ?

You can use this button to go to the Firefox profile folder:

• Help > Troubleshooting Information > Profile Directory: Show Folder

Thanks for all your help guys. I uninstalled and installed the version preconfigured for my locale. Pretty fool-proof way to fix it and it worked. :)