default value does not work :)

hi.
i'm trying for like hours now to set a default value for the cck autocomplete field using this code.

global $user;
$this_user=$user->name
return array(
  0 => array(
    'value' => $this_user,
  )
 );

but with no luck!

i've read the previous posts but the patch at cvs does not seem to work . . . or i am doing something wrong!