That's the hole I am in now. Everything looks good until you actually select a USPS choice and continue. Shipping screen comes back but the USPS section says "An error occured with USPS shipping calculations..." But where did the shipping numbers come from just a few seconds ago?
(I'm seriously thinking of changing that message to "HEY, if you order more than $50 of stuff shipping is free so why not just do that?")
New 
tomt got a reaction from wkdwich in Heads Up: July 28, 2013 USPS Name Change for Express Mail