I have been working on upgrading from 1.3.7 to 1.5.1 and I have run into problems with getting the payment module to work properly.

I have changed the URLs to point to internetsecure
I have removed the hash

The payment goes through but it does not complete the order and returns the site to a page that displays : "Whoops! Your session has expired.
If you were placing an order, please login and your shopping cart will be restored. You may then go back to the checkout and complete your final purchases.

If you had completed an order and wish to review it, or had a download and wish to retrieve it, please go to your My Account page to view your order."

and then logs you out.

InternetSecure emails me the approval and the transaction is completed, however zencart acts as though the payment didn't go through.

Any advise would be helpful.

-Graham