I registered my site on FeedBurner in late November, but never took the time to make it working properly.
The gist of making it work is redirection. To accomplish that, you will need to modify .htaccess file in Apache. I came across a WordPress FeedBurner plugin, which helped me generating the proper .htaccess code. If you have http 500 error, most likely the redirect is doing a recursive lookup. Fix the original feed source in the FeedBurner should fix the problem.
So now the new feed should be alive and working. Please let me know if you have any problems. Your comments are always welcome.