Name check when creating a thread with threadmanager

[squishi]

I am trying to create a new thread with PHP:

PHP Code:

$threaddm =& datamanager_init('Thread_FirstPost', $vbulletin, ERRTYPE_ARRAY, 'threadpost');
        $foruminfo = verify_id('forum', $forum_id, 0, 1);
        $threaddm->set_info('forum', $foruminfo);
        $threaddm->set('forumid', $forum_id);
        $threaddm->registry->options['floodchecktime'] = 0;
        $threaddm->set('username', $username);
        $threaddm->set('title', $title);
        $threaddm->set('pagetext', $pagetext);
        $threaddm->set('allowsmilie', $allowsmilie);
        $threaddm->set('lastposter', $username);
        $threaddm->set('visible', 1);
        $threaddm->set('dateline', $dateline);
        $threaddm->pre_save();
        if(!empty($threaddm->errors))
        {
            var_dump($threaddm->errors);
            die();
        } 


Output:

array(2) { [0]=> string(180) "That username is already in use or does not meet the administrator's standards. If you are admin and you have forgotten your password, click here." [1]=> string(45) "You did not specify a username for your post." }

Yes, the username is admin and I have set this username to be banned and not to be used in new registrations.
However, it makes no sense that vbulletin would not allow me to create a new thread with that username!
What is wrong with the above code?