Postid in newthread

[mad@Max]

Hi to all.
I have this code

PHP Code:

        if ($type == 'thread')
        {
            $mdmdataman = &datamanager_init('Thread_FirstPost', $vbulletin, ERRTYPE_SILENT, 'threadpost');
        } else
        {
            $mdmdataman = &datamanager_init('Thread', $vbulletin, ERRTYPE_ARRAY, 'threadpost');
        }
        $mdmdataman->set_existing($threadinfo);
        $mdmdataman->set('lastreleaseid', $post['postid']);
        $mdmdataman->set('lastrelease', TIMENOW);
        $mdmdataman->save(); 


Included on newpost_complete.

Sometime, when creating a new thread, postid either zero or the default value stored in the field lastreleaseid (i.e., 0).

Where i did mistake?