form_validation->run() Problem

Code:
class Registration extends Controller

{

    function Registration()

    {

        parent::Controller();

        $this->load->scaffolding('cms_users');

        $this->load->helper('url');

        $this->load->helper('form');

        

    }

    function index()

    {

        $this->load->helper(array('form', 'url'));

        $this->load->library('form_validation');

        //ogni errore sarà contenuto nel class div error

        $this->form_validation->set_error_delimiters('<div class="error">', '</div>');

        

        $data['title']="Registrazione Utente";

        $data['heading']="Form di registrazione";

        $data['query']=$this->db->get('cms_users');

        $this->db->select('*');

        $this->db->order_by('name','asc');

        $data['nation']=$this->db->get('cms_nation');

        $this->db->select('*');

        $this->db->order_by('prov_name','asc');

        $data['province']=$this->db->get('cms_province');

        

        //verifico se la registrazione ha degli errori

        //echo $this->form_validation->run();

        

        $this->form_validation->set_rules('surname', 'Cognome', 'trim|required|xss_clean');

        $this->form_validation->set_rules('name', 'Nome', 'trim|required|xss_clean');

        $this->form_validation->set_rules('rag_sociale', 'Ragione Sociale', 'trim|required|xss_clean');

        $this->form_validation->set_rules('nation', 'Nazione', 'trim|required|xss_clean');

        $this->form_validation->set_rules('province', 'Provincia', 'trim|required|xss_clean');

        $this->form_validation->set_rules('zip_code', 'CAP', 'trim|required|xss_clean');

        $this->form_validation->set_rules('city', 'Citt&agrave;', 'trim|required|xss_clean');

        $this->form_validation->set_rules('address', 'Indirizzo', 'trim|required|xss_clean');

        $this->form_validation->set_rules('phone', 'Recapito', 'trim|required|xss_clean');

        $this->form_validation->set_rules('fax', 'Fax', 'trim|required|xss_clean');

        $this->form_validation->set_rules('birth_date', 'Data di Nascita', 'trim|required|xss_clean');

        $this->form_validation->set_rules('email', 'Email', 'trim|required|valid_email|xss_clean');

        $this->form_validation->set_rules('web', 'Sito Web', 'trim|required|xss_clean');

        $this->form_validation->set_rules('gender', 'Sesso', 'trim|required|xss_clean');

        $this->form_validation->set_rules('username', 'Username', 'trim|required|min_length[5]|max_length[12]|xss_clean|callback_username_check');

        $this->form_validation->set_rules('password', 'Password', 'trim|required|md5');

        //$this->form_validation->set_rules('password_conf', 'Ripeti Password', 'trim|required');

        

        if ($this->form_validation->run() == FALSE)

        {

            $this->load->view('registration_view',$data);

        }

        // o se è andata a buon fine

        else

        {

            $this->db->insert('cms_users',$_POST); //insert(db colum,$_POST);

            $this->load->view('registration_success');

        }

    }

}