could someone be kind enough to explain why i am getting the following errors?

in sandbox mode no https - works fine, calculates shipping.

sandbox mode w/ https - i get :

We encountered an error trying to access your server at https://MY-SITE.TLD/googlecheckout/responsehandler.php

-- the error we got is: Sending failed with HTTP response code: 302. Response body was:

so i did some searching and saw a post mentioning the response handler test. this is what i get from that :

Code:
Authorization: Basic XXXXXX:XXXXXX
Content-Type: application/xml;charset=UTF-8
Accept: application/xml;charset=UTF-8
X-Origin-IP: 70.253.43.238
Code:
HTTP/1.0 405 Method Not Allowed
Server: Zeus/4.3
Date: Wed, 19 Sep 2007 19:35:05 GMT
Allow: GET, HEAD
Content-Type: text/html
Hostname: b015
X-Cache: MISS from proxy.globant.com
Proxy-Connection: close

<html><head><title>Error 405 Method Not Allowed
</title></head><body bg##############################><h2>Error 405 Method Not Allowed
</h2><p>The requested method POST is not allowed for URL /googlecheckout/responsehandler.php<p><i>Powered by <a href="http://errors.zeus.com/">Zeus Technology</a></i></body></html>
and i get the same in production mode....

any help would be greatly appreciated. I tried asking help from google but they said
since its integrated with zen cart. i need to ask them.

Thanks,

James