on the confirm page, add the following code just after the <body> tag:
<?php
if(!session_id()) session_start();
echo "<p>USPS: <br />";
echo "Full Request: ".(isset($_SESSION["store1_USPS_FullRequest"])?htmlentities($_SESSION["store1_USPS_FullRequest"]):"n/a")."<br />";
echo "Full Response: ".(isset($_SESSION["store1_USPS_FullResponse"])?htmlentities($_SESSION["store1_USPS_FullResponse"]):"n/a")."<br /></p>";
?>
this will add the full request and response being sent to the shipping provideer to the page and help us see what is going on.