I've found out some new infos on this bug. If I delete the configuration file :
~/.mozilla/firefox/rq2c5y0w.default/compatibility.ini I can get the download funcion again for the next session of firefox. When I load firefox after having deleted this file this message appears in console : *** loading the extensions datasource *** loading the extensions datasource This message doesn't appear when the compatibility.ini file is already present at load time. Closing this session and reloading firefox again (without deleting the new file compatibility.ini file created ) makes the download function unavailable again Bye Marcello
