If what dr del suggested doesn't work, try this:

I know you said you already uninstalled and reinstalled firefox. However, sometimes when you "uninstall" a program, there are files leftover (such as preference files, bookmark files etc) that keep old issues around when you reinstall.

The trick is to uninstall, and manually delete all content related to that program before reinstalling. So after you uninstall, go to where firefox is installed and delete the "Mozilla Firefox" folder and all the files inside. Then reinstall. This should then be a 100% clean reinstall with no leftover issues from before.