I am running Firefox 20 FRENCH (this is maybe important as all of this below does not appear with the EN version...) on MacOSX 10.6.8. Symptoms : - Web Developer toolbar not displayed anymore. - Xmarks add-ons not displayed in the module bar. - Icons of other add-ons displayed in the navigation bar ONLY after the first firefox opening i.e. just after system restart. If firefox is closed and re-opened, all the add-ons icons are lost. > All the add-ons are installed in tha add-on menu. > This behavior only appear with the FRENCH versions of firefox (tried 19.0.2 and 20). > Installed the 19.0.2 ENGLISH version and all is OK !!! Fixes attempts (tried almost everything...) : - Reset firefox profile and restart with a new one : no effect (after I have reinstalled all the add-ons one by one...) - Uninstall Firefox (with profiles folder, cache folders, etc...) then reinstall : no effect - The only thing that is working is using the ENGLISH version... This is really annoying because as a web developer I really need the Web Developer extension. Does anyone has an idea of how to fix this ? Thank you very much for your help ! Regards,