Need more info, man...
Did you have Firefox closed during installation of the update (to let it install correctly), or did you install while Firefox was still running (and you clicked "Postpone" when Sticky notified you that Firefox is still running)?
Are BOTH the extension AND the plugin installed correctly? Are their versions correct?
Is it perhaps the same situation which you had last time (viewtopic.php?f=79&t=74330&p=84803#p84803
P.S. There is nothing like SP help file for SP6... where exactly did you try to search?!