The default language on Firefox somehow changed from Italian to Japanese. I did not reinstall Firefox, I can't think of anything that I did that could've changed the default language, especially because now I can't seem to change it. I have reinstalled the Italian language pack and placed it at the top of my preference list, but Japanese is still there and I cannot remove it (the button is greyed out). Some extensions are broken because they look at the default language and not at the current in-use preferred language. How can I change the default language without having to reinstall Firefox?