Help with User Registration Function?

[eluser]GSV Sleeper Service[/eluser]
a blank page often means that you've got some whitespace after the closing PHP tag, most of the time the closing tag is not necessary, leave it out to avoid potential problems.

I can't see register_player() being called anywhere, the sensible place to call it would be here

Code:

if ($this->form_validation->run() == FALSE)
{
  $this->load->view('register');
}
else
{
  //register the user
  $this->register_player();
  //show the form success
  redirect('form/success/');
}

if you do go this route you'll need to remove the redirect() from register_player() and replace it with a return.
you're almost there with the username_check() callback, if you're checking for duplicate usernames you'll have to perform the relevant query, at the moment you're selecting ALL the usernames from the player table