feedburner and wp-rss2.php

and atom for that. Feedburner won’t validate the feed. it comes back with
Aw, shoot. There was some trouble retrieving the feed you requested.

HTTP Error Code: 500

Detail: There was a problem retrieving the feed: resource http://gvlshornbook.gnuker.com/wp-rss2.php did not return a proper response

What to do?
You may contact us to report the problem. Please include the feed address error code and message detail displayed above in your message to us, if possible.

You may also try your original request or action again in case the error was just a momentary blip.

Can you help em solve this?