You need to set iFrame template for your X-Cart 5 shop in X-Payments, too.
Right now you have iFrame enabled at X-Cart side, but X-Payments is configured to display template for standalone page.
See
https://docs.google.com/a/x-cart.com/file/d/0B6p7sehSZL8_VnAwT3pUeFFHR0k/edit?usp=drivesdk