Pb when inserting in DB

[eluser]FranckRR[/eluser]
Hello guys,

controller :

Code:

....
$this->load->model('Activities');
$this->Activities->date_activity = $this->input->get_post['dateActivity'];
...
$this->Activities->insert();
$this->load->view('activitiesInserted');
....

Model:

Code:

...
var $date_activity   = '';
    function insert(){
        $this->db->insert('activities');
    }
...

What's wrong ?

Error prompted

Code:

A Database Error Occurred
Error Number: 1054

Unknown column '_ci_ob_level' in 'field list'

INSERT INTO `activities` (`id`, `date_creation`, `date_activity`, `town_id`, `activity_id`, `description`, `duree`, `paye`, `amount`, `currency_id`, `fichier_joint`, `_ci_ob_level`, `_ci_view_path`, `_ci_is_php5`, `_ci_is_instance`) VALUES ('', NULL, '2010-07-07', '17', '5', NULL, NULL, 0, NULL, NULL, NULL, 0, '/mnt/164/free.fr/0/6/fraberegis/florida2010/system/application/views/', 0, 0)