Aom doesnt work on wordpress 2.51 why?

Heelo i would like to know when I used firefox nd click on atom symbol near url : http://olivierbaudrydesign.free.fr i can see this :

http://olivierbaudrydesign.free.fr/?feed=atom

ERREUR : atom n’est pas un flux valide

in my header i have this :<link rel="alternate" type="application/atom+xml" title="Atom 0.3" href="<?php bloginfo('atom_url'); ?>" />