Technically, this is not a FeedBurner issue. I checked a blog that uses the old FeedBurner, and its feed appears to be fine.
But is is a FeedProxy issue?
I began nosing around on the Blogger end of things, and found this:
Try entering your feed URL into FeedValidator.org to see if there are any problems with it.
So I entered http://feedproxy.google.com/Empoprise-bi into FeedValidator.org, and was informed that this IS a valid Atom 1.0 feed.
I then ended up here and tried pinging my Empoprise-BI and Empoprise-MU feeds. I was informed that both feeds were successfully pinged...but my newer content still didn't show up.