Pg_dump postgreSQL 8.1.3-1 and win2k

["Séguier, Géraldine" <Geraldine(dot)Seguier(at)spotimage(dot)fr>]

I'm trying to dump a schema and I receive this error :

pg_dump: Error message from server: ERROR: permission denied for relation pg_ts_dict

pg_dump: The command was: LOCK TABLE public.pg_ts_dict IN ACCESS SHARE MODE
pg_dump: *** aborted because of error

The schema was created by a superuser "X", and the dump has been done by another user "Y" which has the privileges : ALL on this table.

grant ALL on table pg_ts_dict to Y;

The owner of pg_ts_dict is "X".

Thanks for your answer,