OK. It looks like we're going to have to do some serious debugging.
Put
<?php
drupal_set_message('<pre>'. htmlentities($request) .'</pre>');
?>after line 602, put
<?php
drupal_set_message('<pre>'. htmlentities($resp->data) .'</pre>');
?>after line 603, and maybe also put
<?php
drupal_set_message('<pre>'. print_r($response, true) .'</pre>');
?>after line 608.
After you do that, refresh the checkout screen, enter a valid postal code and try to calculate the shipping cost. It should still not work, so refresh the page again so we can see all the messages that were generated. There may or may not be a lot of them, but since they're long, I only want the first set of 3.
Joined: 08/07/2007