I should also mention that in the image I attached above, there is no time-in-transit information next to the USPS shipping methods. That implies to me that either you don't have the latest USPS module installed or maybe there is a bug in the transit time request to the USPS server - if the transit time stuff is failing it might also account for the xml errors you're reporting. FWIW, transit time works for me on the Beta 1 build 728.