Hi John,
I just tried to re-produce this error on my test portal and was unable to recreate the error but I cannot test of the same version you are running and I may not have the exact same configuration as you. Can you login to our test site http://www7.smith-consulting.com/ and try to replicate the error. This will determine if the issue is with the latest version of the cart or an issue with your specific dnn portal/cart install. Please email me at kevin@smith-consulting.com for login credentials.
Thanks,