I'm OWNER of the db but I get `permission denied` when doing updating table pg_class ???? Any help appreciated

Hi all,

I just created a new db wich userX is owner.  I log via pgAdminIII with
the same user but I can't update the pg_class.

UPDATE pg_class SET reltriggers = 0 WHERE relname = 'ic'

I get:ERROR:  permission denied for relation pg_class

I do that on my dev env.  The only difference I saw beetween users is
that my DEV user as priviledge to create database(But it shouln't
matter...?!)

We create the db with : createdb -O userX -E UNICODE webCatalogTest

Thanks for your help!

/David