[kh99]

The fields shouldn't be blank. I think the problem is that at the newpost_process hook the new thread hasn't been created yet. When that hook code runs, there is an existing Thread_Firstpost data manager, so you probably want to use that instead of creating your own thread data manager. So when you add the valid fields, use hook threadfpdata_start instead of threaddata_start. Then at newpost_process, try just doing this:

if ($type == 'thread')
{
    $dataman->setr('domainforsalename', $post['domainforsalename']);
    $dataman->setr('domainforsalebnprice', $post['domainforsalebnprice']);
}