If you bought The Dip from iTunes and are having trouble making it play on your iPod, please drop me a line. Put "iPod" in the subject line. Apple is working to fix a glitch, and I’ll email you when I’m alerted that it’s been fixed. If you’ve been thinking of buying the audio version with the intent of playing it on your iPod, please wait a bit. Thanks. And I apologize for the hassle.
[UPDATE: this has been fixed, I’m told! If you didn’t get a refund, please email Apple directly and insist. And judging from the mail I’ve gotten, it should be safe to try again. Thanks for your patience.]