plugin that creates a thread when a post has been made in a certain topic

[Schwartz12]

Been Playing around with this code:

hook location: newpost_complete

$postforumid = 4;
$postforum = fetch_foruminfo($postforumid);

$post['title'] = "here is my catchy title";
$post['message'] = "some fabulous message.";


build_new_post('thread', $postforum , array(), array(), $newpost, $errors);


What I get with this is the following error above a new reply form; why, I don't know though I expect it may be because of some crossover with the variables or something

The following errors occurred when this message was submitted:
Please complete both the subject and message fields.
The message you have entered is too short. Please lengthen your message to at least 10 characters.

and the "here is my catchy title" and "some fabulous message" are inputted into the form

Any help would be appreciated.

Thanks!