Tank Auth v1.0 (CI authentication library)

[eluser]bondjp[/eluser]
Hi guys,
I'm trying to add fields to user_profiles table but i'm having trouble doing it.
When i insert the 'firstname' and 'lastname' i get 2 records in the user_profiles table.
One record is id='1' user_id='1' firstname=Blank lastname=Blank
Second record id='2' user_id='0' firstname='Bob' lastname='Warner'

Here's the part where i insert the values:

Code:

if ($this->form_validation->run()) {                                // validation ok
            if (!is_null($data = $this->tank_auth->create_user(
        $use_username ? $this->form_validation->set_value('username') : '',
            $this->form_validation->set_value('email'),
        $this->form_validation->set_value('password'),
        $email_activation))) {                                    // success
                        $firstname=$this->form_validation->set_value('firstname');
$lastname=$this->form_validation->set_value('lastname');
$userprofile = array('firstname' => $firstname,'lastname' => $lastname);
$this->db->insert('user_profiles', $userprofile);

I appreciate any help.
Thanks.