Quite a while back the feed URL for this blog changed back to the default Blogger one. I've been using FeedBurner from day one but Blogger initially didn't have the ability to redirect to a different URL for your feed.
I've noticed that few subscribers are still directly using the old FeedBurner URL. When you find the time please update your reader to use the canonical URL:
I don't expect the old one to go away any time soon but better to be safe than sorry.