To tell you the truth this error is not one that I have seen before, nor any like it. It seems to be saying that the xml is malformed and not accepted by the api.
When you talked to USPS what type of account did they open for you? Did you get a new production server URL to post to? If so what is that new URL? If you have not been given the production URL from USPS you should try to login and obtain the one that they are listing for you and post back with this value.