Did Apple email you about the problem? Do you happen to recall the particular Feedburner setting (we use Feedburner, too.) I did get one email at the very beginning about a validation failure. I resolved that and haven’t heard anything since. We were going to try having my co-host submit the feed in case it was a problem with my account. If it’s a known issue with Feedburner, though, that would explain a lot and would hopefully be easy to fix.