I think I saw this exact same error when trying to buy the Business Edition of Google Custom Search. It took an email to customer support to get it fixed (I emailed Friday, and it was fixed on Monday, so not a terrible turnaround on solving the problem)...though I never knew what was wrong, because the error was absolutely devoid of meaning.
There are so many things that suck about Google Checkout that it's just pointless to rant. Chris could spend the next two months, I bet, writing "Google Checkout: How Not to..." posts.
I love the intelligent comments below the article. A particularly insightful gem:<p><pre><code> Google sucks !
</code></pre>
Amazing that he can't even get the punctuation right on a two-word sentence.