I can confirm that this is an issue with my live code as well. http://shop.rifftrax.com.

If you fill out your information (but leave something "required" blank) and go to Review your order, the POST information from your shipping quote form seems to not carry through.

It seems to "remember" that you had already fulfilled that information, but "forget" it at the same time. I haven't done any digging, since the easiest thing to do is to just hit the checkout button again and this time, remember to fill in all the required fields...