I was using google-checkout-java-sdk in a custom online shopping solution. When I switched the project's POM from java 1.5 to 1.6, it seems that google checkouts would no longer work. I was getting this error when attempting to send an order to Google Checkout:
The root of this problem was difficult to find, but with some googling it sounds like it has something to do with changes in Sun's rt.jar. I experimented with removing xerces dependencies or using different versions of it (2.0.2, 2.9.1). That didn't work. So then I added xalan-2.7.1 to my POM, and things started to work again!
I haven't really gotten to the root of this yet, but at least I can make my client happy again. Would love to hear from anyone who knows more about this.