I am having this same issue. Here is more info:
When I use it after payment is finished on the qchex, it redirects me to my oscommerce sit, but to the login.php page rather than checkout_process or success, and therefore doesn?t log the transaction to the admin. I do use the checkout without account (but I still believe this till creates an account, just not login/password, and it still has an oscommerce id). Any ideas to get this to work? I can pay you for your time if you give me an estimate.