I use Tab Mix Plus When I right-click a tab, the menu doesn't show the menu items for Tab mix plus. I had the same problem with all addon items in the Firefox menu not showing up (they didn't show up under Open menu|Customise either. I backed everything up with addon FEBE, reset firefox, then restored everything with FEBE and this fixed the menu items. The reset and restore also fixed another problem where the icons for new addons weren't showing up in the row of icons next to the search bar (don't know what those are called). I also can't login to this support site in firefox - it keeps telling me to create an account - and so am using another browser for this message and have manually added troubleshooting Information.