So I fixed my RSS and Atom feeds on this Wordpress 2.5 powered blog.  Apparently there was an extra blank line in one of my theme function files.  This put a blank line at the top of the XML documents making them invalid.

Interestingly, it also fixed the issue I was having with the Visual editor not working for new posts.  I have been beating my head against the wall for a few days on that one.  All better now!