secure site question

I'm having a problem and I'm not quite sure what the best way to solve it is so I'm looking for some guidance. I have an e/COMMERCE site that uses sessions named www.xxx.com. The final step (payment) involves getting credit card information so I bop over to https://secure.xxx.com which serves up the page correctly. The problem is that it knows nothing about my previous session so the cart and login information is no longer there. How can I let the secure page know what's going on with the order? I'm trying to avoid a kludge here so I'm hoping someone has already faced this problem. Thanks