[kh99]

I think the problem is that $this->post['usergroupid'] is not set if it's a pm (and so you can't use is_member_of(), if that's what you're doing). I don't think there's anything you can do except do a query for it yourself if you're displaying a PM. Maybe something like:

if (get_class() == 'vB_Postbit_Pm')
{
   $userinfo = fetch_userinfo($this->post['userid']);
}
else
{
   $userinfo &= $this->post;
}

// then use $userinfo to check group...