Sorry, it looks like I got the capitalization on your eCart object incorrect when I sent you the code. Try this code instead:
<?php
echo "<p>USPS: <br />";
echo "Full Request: ".(isset($_SESSION["SaleCo_USPS_FullRequest"])?htmlentities($_SESSION["SaleCo_USPS_FullRequest"]):"n/a")."<br />";
echo "Full Response: ".(isset($_SESSION["SaleCo_USPS_FullResponse"])?htmlentities($_SESSION["SaleCo_USPS_FullResponse"]):"n/a")."<br /></p>";
?>