I would like to have you login to one of our public test portals and configure the cart the way you have your's configured and try to replicate the issue.
This will determine if the issue you are reporting is with the latest version of the module or an issue with your specific DNN portal/module install.
Please submit a Help Desk request with a link to this post at the following link and we will provide you with credentials to log in:
http://helpdesk.smith-consulting.com/...
Thanks!