SESSION and SSL

[madproject.com]

I've got a cart that stores the information in an object that is stored in the session like so:

  include("cart.php");
  session_start();
  $cart =& $_SESSION['cart'];
  if(!is_object($cart)) $cart = new Cart(); 

Everything works fine, but when the person checks out and goes to a secure area, it looses the contents.

HOWEVER, if the person rebuys the stuff again and checks out, it'll work that time. It just doesn't work the first time!

What could cause this?

[madproject.com]

Anybody?