After spending hours and hours and hours, almost a full day, working on this... I think I finally was able to get GoogleCheckout's Payment Module to recognize my greatness... Or at least semi-work. My problem is that before I claim total victory, I am no longer receiving error messages about something being wrong with the XML but.. just a generic We were unable to process your request." I've already written the GoogleCheckout Team but while I wait, figured I'd also ask here. One small caveat on this whole thing is that this is being called from a localhost, my personal webserver, while I test and make mods to the site before going live.

Here is a copy of the XML that is being outputted but after going over Google Checkout's XML documentation, I can't figure out if it's me, the XML, or that Google doesn't like dealing with "localhost"

Thanks in advance.

Code:
<?xml version="1.0" encoding="UTF-8"?>
<checkout-shopping-cart xmlns="http://checkout.google.com/schema/2">
  <shopping-cart>
    <items>
      <item>
        <item-name>Yoga Mastery [SF01 36]</item-name>
        <item-description></item-description>
        <unit-price currency="USD">0.5</unit-price>
        <quantity>4</quantity>
        <merchant-private-item-data>
          <item>YToxNjp7czozOiJxdHkiO2k6NDtzOjQ6Im5hbWUiO3M6MjI6IllvZ2EgTWFzdGVyeSBbU0YwMSAzNl0iO3M6NToibW9kZWwiO3M6MTE6IlVGUzBTRjAxMDM2IjtzOjM6InRheCI7aTowO3M6MTA6InRheF9ncm91cHMiO2E6MTp7aTowO3M6OToiU2FsZXMgVGF4Ijt9czoxNToidGF4X2Rlc2NyaXB0aW9uIjtzOjk6IlNhbGVzIFRheCI7czo1OiJwcmljZSI7czo2OiIwLjUwMDAiO3M6MTE6ImZpbmFsX3ByaWNlIjtkOjAuNTtzOjE1OiJvbmV0aW1lX2NoYXJnZXMiO2k6MDtzOjY6IndlaWdodCI7ZDowLjAwMTAwMDAwMDAwMDAwMDAwMDAyMDgxNjY4MTcxMTcyMTY4NTEzMjk0MzA5Mzc3NjcwMjg4MDg1OTM3NTtzOjI4OiJwcm9kdWN0c19wcmljZWRfYnlfYXR0cmlidXRlIjtzOjE6IjAiO3M6MTU6InByb2R1Y3RfaXNfZnJlZSI7czoxOiIwIjtzOjIyOiJwcm9kdWN0c19kaXNjb3VudF90eXBlIjtzOjE6IjAiO3M6Mjc6InByb2R1Y3RzX2Rpc2NvdW50X3R5cGVfZnJvbSI7czoxOiIwIjtzOjI6ImlkIjtpOjE0OTc7czo4OiJyb3dDbGFzcyI7czo3OiJyb3dFdmVuIjt9</item>
        </merchant-private-item-data>
        <merchant-item-id>1497</merchant-item-id>
        <tax-table-selector>Taxable Goods</tax-table-selector>
        <item-weight unit="LB" value="0.001" />
      </item>
    </items>
    <merchant-private-data>
      <session-data>omvq9rlda49jj2kc5akvj2t3v7;zenid</session-data>
      <ip-address>127.0.0.1</ip-address>
    </merchant-private-data>
  </shopping-cart>
  <checkout-flow-support>
    <merchant-checkout-flow-support>
      <edit-cart-url>http://localhost/zencart/index.php?main_page=shopping_cart</edit-cart-url>
      <continue-shopping-url>http://localhost/zencart/index.php?main_page=checkout_success</continue-shopping-url>
      <shipping-methods>
        <merchant-calculated-shipping name="United States Postal Service (0.06lbs): Express Mail (1 - 2 days)">
          <price currency="USD">21.05</price>
          <shipping-restrictions>
            <allow-us-po-box>true</allow-us-po-box>
            <allowed-areas>
              <us-country-area country-area="ALL" />
            </allowed-areas>
          </shipping-restrictions>
          <address-filters>
            <allow-us-po-box>true</allow-us-po-box>
            <allowed-areas>
              <us-country-area country-area="ALL" />
            </allowed-areas>
          </address-filters>
        </merchant-calculated-shipping>
        <merchant-calculated-shipping name="United States Postal Service (0.06lbs): First-Class Mail (2 - 5 days)">
          <price currency="USD">1.39</price>
          <shipping-restrictions>
            <allow-us-po-box>true</allow-us-po-box>
            <allowed-areas>
              <us-country-area country-area="ALL" />
            </allowed-areas>
          </shipping-restrictions>
          <address-filters>
            <allow-us-po-box>true</allow-us-po-box>
            <allowed-areas>
              <us-country-area country-area="ALL" />
            </allowed-areas>
          </address-filters>
        </merchant-calculated-shipping>
        <merchant-calculated-shipping name="United States Postal Service (0.06lbs): Priority Mail (2 - 3 days)">
          <price currency="USD">5.25</price>
          <shipping-restrictions>
            <allow-us-po-box>true</allow-us-po-box>
            <allowed-areas>
              <us-country-area country-area="ALL" />
            </allowed-areas>
          </shipping-restrictions>
          <address-filters>
            <allow-us-po-box>true</allow-us-po-box>
            <allowed-areas>
              <us-country-area country-area="ALL" />
            </allowed-areas>
          </address-filters>
        </merchant-calculated-shipping>
        <merchant-calculated-shipping name="United States Postal Service (0.06lbs): Express Mail International (3 - 5 business days)">
          <price currency="USD">28.95</price>
          <shipping-restrictions>
            <allow-us-po-box>true</allow-us-po-box>
            <allowed-areas>
              <world-area />
            </allowed-areas>
            <excluded-areas>
              <postal-area>
                <country-code>US</country-code>
              </postal-area>
            </excluded-areas>
          </shipping-restrictions>
          <address-filters>
            <allow-us-po-box>true</allow-us-po-box>
            <allowed-areas>
              <world-area />
            </allowed-areas>
            <excluded-areas>
              <postal-area>
                <country-code>US</country-code>
              </postal-area>
            </excluded-areas>
          </address-filters>
        </merchant-calculated-shipping>
        <merchant-calculated-shipping name="United States Postal Service (0.06lbs): Express Mail International Flat Rate Envelope (3 - 5 business days)">
          <price currency="USD">28.95</price>
          <shipping-restrictions>
            <allow-us-po-box>true</allow-us-po-box>
            <allowed-areas>
              <world-area />
            </allowed-areas>
            <excluded-areas>
              <postal-area>
                <country-code>US</country-code>
              </postal-area>
            </excluded-areas>
          </shipping-restrictions>
          <address-filters>
            <allow-us-po-box>true</allow-us-po-box>
            <allowed-areas>
              <world-area />
            </allowed-areas>
            <excluded-areas>
              <postal-area>
                <country-code>US</country-code>
              </postal-area>
            </excluded-areas>
          </address-filters>
        </merchant-calculated-shipping>
        <merchant-calculated-shipping name="United States Postal Service (0.06lbs): Priority Mail International Small Flat Rate Box (6 - 10 business days)">
          <price currency="USD">13.45</price>
          <shipping-restrictions>
            <allow-us-po-box>true</allow-us-po-box>
            <allowed-areas>
              <world-area />
            </allowed-areas>
            <excluded-areas>
              <postal-area>
                <country-code>US</country-code>
              </postal-area>
            </excluded-areas>
          </shipping-restrictions>
          <address-filters>
            <allow-us-po-box>true</allow-us-po-box>
            <allowed-areas>
              <world-area />
            </allowed-areas>
            <excluded-areas>
              <postal-area>
                <country-code>US</country-code>
              </postal-area>
            </excluded-areas>
          </address-filters>
        </merchant-calculated-shipping>
        <merchant-calculated-shipping name="United States Postal Service (0.06lbs): Priority Mail International Flat Rate Envelope (6 - 10 business days)">
          <price currency="USD">13.45</price>
          <shipping-restrictions>
            <allow-us-po-box>true</allow-us-po-box>
            <allowed-areas>
              <world-area />
            </allowed-areas>
            <excluded-areas>
              <postal-area>
                <country-code>US</country-code>
              </postal-area>
            </excluded-areas>
          </shipping-restrictions>
          <address-filters>
            <allow-us-po-box>true</allow-us-po-box>
            <allowed-areas>
              <world-area />
            </allowed-areas>
            <excluded-areas>
              <postal-area>
                <country-code>US</country-code>
              </postal-area>
            </excluded-areas>
          </address-filters>
        </merchant-calculated-shipping>
        <merchant-calculated-shipping name="United States Postal Service (0.06lbs): First-Class Mail International Package (Varies by country)">
          <price currency="USD">2.28</price>
          <shipping-restrictions>
            <allow-us-po-box>true</allow-us-po-box>
            <allowed-areas>
              <world-area />
            </allowed-areas>
            <excluded-areas>
              <postal-area>
                <country-code>US</country-code>
              </postal-area>
            </excluded-areas>
          </shipping-restrictions>
          <address-filters>
            <allow-us-po-box>true</allow-us-po-box>
            <allowed-areas>
              <world-area />
            </allowed-areas>
            <excluded-areas>
              <postal-area>
                <country-code>US</country-code>
              </postal-area>
            </excluded-areas>
          </address-filters>
        </merchant-calculated-shipping>
        <merchant-calculated-shipping name="United States Postal Service (0.06lbs): First-Class Mail International Large Envelope (Varies by country)">
          <price currency="USD">2.08</price>
          <shipping-restrictions>
            <allow-us-po-box>true</allow-us-po-box>
            <allowed-areas>
              <world-area />
            </allowed-areas>
            <excluded-areas>
              <postal-area>
                <country-code>US</country-code>
              </postal-area>
            </excluded-areas>
          </shipping-restrictions>
          <address-filters>
            <allow-us-po-box>true</allow-us-po-box>
            <allowed-areas>
              <world-area />
            </allowed-areas>
            <excluded-areas>
              <postal-area>
                <country-code>US</country-code>
              </postal-area>
            </excluded-areas>
          </address-filters>
        </merchant-calculated-shipping>
      </shipping-methods>
      <request-buyer-phone-number>true</request-buyer-phone-number>
      <tax-tables merchant-calculated="false">
        <default-tax-table>
          <tax-rules>
            <default-tax-rule>
              <shipping-taxed>false</shipping-taxed>
              <tax-area>
                <postal-area>
                  <country-code>US</country-code>
                </postal-area>
              </tax-area>
            </default-tax-rule>
          </tax-rules>
        </default-tax-table>
        <alternate-tax-tables>
          <alternate-tax-table standalone="false" name="Taxable Goods">
            <alternate-tax-rules>
              <alternate-tax-rule>
                <tax-area>
                  <postal-area>
                    <country-code>US</country-code>
                  </postal-area>
                </tax-area>
              </alternate-tax-rule>
            </alternate-tax-rules>
          </alternate-tax-table>
        </alternate-tax-tables>
      </tax-tables>
      <rounding-policy>
        <mode>HALF_EVEN</mode>
        <rule>TOTAL</rule>
      </rounding-policy>
    </merchant-checkout-flow-support>
  </checkout-flow-support>
</checkout-shopping-cart>