@greenbocai,

I'll take a look and send you an email shortly.

[UPDATE: somewhat long and somewhat complicated issue, but the short version is that subscribers who download MP3 and PDF files are now downloading them directly from our server so we can configure them on-the-fly into traditional/simplified and include or omit english/pinyin, etc. based on people's customizable display settings.

It turns out that iTunes was having difficulty identifying the links to some of these mp3 and pdf files as valid, even though they were valid. I've made some tweaks that seem to keep iTunes happy.

If anyone else is having this problem, you should be able to solve it by just refreshing the feed in iTunes]

Thanks,

--david