Hi Tim,
I have setup a similar scenario on my test portal and tried re-produce this issue but I was unable to recreate the behavior you reported, however I may not have the exact same configuration as you. 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 cart or an issue with your specific dnn portal/cart install.
Please send an email with a link to this post to
kevin@smith-consulting.com and I will provide you with credentials to login.
Thanks