[Sparkle] Sparkle not working

[Thomas Worrall]

I have created a test update to my app, and it downloads and extracts  
it OK. But it then gives an error when installing it. Upon  
investigation, what has happened is Sparkle has put the entire new  
(updated) app package inside another package of the same name, like so:

iBell.app / iBell.app / contents / ...

When you click on the outer package, the MacOS gives an error for a  
broken package.

What am I doing wrong? The appcast is located at http:// 
www.pointandcode.com/ibell/appcast/iBellAppcast.xml


Thanks.

Thomas