can't restart session

Hello, PHP 4.2.2 I'm working on a cart program right now and I can't properly log the user out. The only way I've been able to get a different session id is by closing all browser windows and reloading the site. Scenario: I go the site I'm working on and click the login page. I have 'echo session_id();' in the login page so I can see the session id. I fill in my username and password and click "login". I'm then sent to a processing page that actually fills in the session variable with some data (i.e. username, session id, security level, etc.). I then redirect back to the login page with header("Location: login.php");. Now that I'm back at the login page I still see my session id (and as expected it is the same). Then I click "logout" and am taken to a logout page. The logout page is as follows: <? // start the customers session session_start(); session_destroy(); setcookie("user_info","",(time()-3600),"/"); header("Location: {$_SERVER["HTTP_REFERER"]}"); exit; ?> Here is another version of the same file that I've tried using: <? // start the customers session session_start(); session_unset(); session_destroy(); header("Location: {$_SERVER["HTTP_REFERER"]}"); exit; ?> As far as I have been able to find out (by surveying other people and RTFM'ing) I'm doing it correctly, but for some it's just not working. After I click logout I would expect to be sent back to the login page and see a different session id displayed, but instead I'm presented with the same session id. The only way I can get a different session id is by closing all the browser windows and starting over. Anyone have any ideas? Thanks, Chris.