"Hervé" wrote...
> i use firefox 3.0.1 and today it's impossible for me to add/update or delete an addon.
>
> after each restart of firefox, i have always the same message, restart firefox for installing...

Hi hervé ,
delete or rename the following in your profile:
extensions.ini
extensions.cache
extensions.rdf

reference for additional information:
http://kb.mozillazine.org/Unable_to_...ions_-_Firefox

--
HTH,
David McRitchie, extensions I use are briefly documented on my site
Firefox Custom: http://www.mvps.org/dmcritchie/firefox/firefox.htm