is there any known bug in session lib of codeigniter 2.1.0 ?

[eluser]Unknown[/eluser]
hi
im working on a website which is created with CI 2.1.0.

the thing i've notice is sometimes when i reload a page couple of time or open couple of pages very fast i get logged out .

this website is using a lib called Ion_authand for identifications

Code:

public function logged_in()
{
  $identity = $this->ci->config->item('identity', 'ion_auth');
  return (bool) $this->ci->session->userdata($identity);
}

is there a bug or something that i should know about ?

Code:

$config['sess_cookie_name']  = 'cisession';
$config['sess_expiration']  = 7200;
$config['sess_expire_on_close'] = TRUE;
$config['sess_encrypt_cookie'] = FALSE;
$config['sess_use_database'] = TRUE;
$config['sess_table_name']  = 'cisession';
$config['sess_match_ip']  = FALSE;
$config['sess_match_useragent'] = TRUE;
$config['sess_time_to_update'] = 300;