iTunes "does not seem to be a valid Podcast URL" error. Why?!!!

[JoshBrahm]

My podcast source xml is http://prolifepodcast.net/media/LifeReport.xml
My feedburner feed, and the one that I send to iTunes is
http://feeds.feedburner.com/LifeReport

Everything has been going fine for 20+ episodes, and then suddenly
iTunes has been acting weird lately. Currently, even though the
Feedburner feed is fine and up to date, iTunes gives me "Life Report:
Pro-Life Answers for a Pro-Choice World" does not seem to be a valid
Podcast URL. Please check that you entered the correct URL and try
again."

Feedvalidator.org only gives me a warning about
"Your feed appears to be encoded as "UTF-8", but your server is
reporting "US-ASCII"

I have no clue how to fix this, but am skeptical that it's the problem
iTunes is having, since I've ALWAYS received that warning from
feedvalidator.org, and it's never been a problem. I need help!!!

[JoshBrahm]

Ironically, my podcast appears in the iTunes store as up-to-date, with
Episode 23 (our latest episode) showing, but when I subscribe, it
doesn't come up in my own podcasts.