Google Checkout Issues

I am having issues with Google Checkout, whenever I place an order, it goes thorough in Google Checkout but is not posting to the store.

Here is the error I get from Google:

We encountered an error processing your notification acknowledgment. The error we got is: Error parsing notification acknowledgment.

When I go back to the store from Google, it goes back to the cart page and an error comes up saying the order was not placed.

I am running CS Cart 3 Ultimate.

Google Checkout was setup using the instructions from the KB article and is running API Version 2.0 and XML notification.