Since my update to wp 3 I had froze in the admin
Looking at the code, I saw my entirely user list was load is the code, instead of the admin and authors.
The error come from the function :
return $wpdb->get_col( $wpdb->prepare("SELECT user_id FROM $wpdb->usermeta WHERE meta_key = %s AND meta_value = '0'", $level_key) );
The meta selected is incorrect,