Feeds not working

Hello everyone,

I upgraded my WP installation from 1.2 to 1.5 and later to 1.5.1.
After the upgrade from 1.2 to 1.5, my RSS/Atom feed stopped working. It only shows the channel informations, but no posts :-/
The url of my RSS2 feed is: http://blog.kaufmann.ws/?feed=rss2
If anyone has an idea what could be wrong with my installation, I would be happy to know it… I tried a few “solutions” I’ve found with google but nothing helped so far 🙁