After upgrading Serendipity, I remembered that the Serendipity developer that helped me out had an Amazon.de wishlist which I had tried to get him something from. The challenge is documented in German in an entry in Garvin Hicking's blog. In fact, it is also documented in this blog in another entry. Anyhow, I retried the process and I think that I may have just completed an Amazon.de wishlist transaction in German. I hope that it works.