Actually the same problem is with me. I've written to Amazon customer service but they can't solve my question.
I got to know there is someone in Switzerland had the same problem and finally solved by calling Amazon technician.
You can see the post here:
http://www.kindleboards.com/index.php?topic=15500.0
I'm a little worried about my spoken English. So I haven't do the calling yet.
Wish you good luck!