Session not working in 1 computer

My sessions work on all computers except 1 computer. It sets the session variable, but when you go back, the data doesn't exist in the session. I tried setting cookies in PHP and those worked fine. I checked all the windows settings for cookies and they are all allowed. I also tried having Codeigniter use a database for sessions and that didn't work either, even though I see the session data stored in the database. It makes no sense. What could possible cause Codeigniter sessions not to work on just that 1 specific computer? Thanks!

This is my test script:

Code:

if (isset($_GET['cookiecheck'])) {

   print_r($this->session->userdata);

} else {

   $cookie_data = array('valid' => true, 'name' => "My Name");

   $cookie_data = array('cookie' => $cookie_data);

   $this->session->set_userdata($cookie_data);

   die(header("Location: http://myurl.com/test?cookiecheck=1"));

}