After spending the day re-ripping and re-building with ABB 1.1, the new audiobooks still don't play correctly on my ipod, although they do appear to be working in QT now.
When there is exactly 5 seconds remaining, the book stops playing and the audiobook menu is displayed. This happens with both single and multi-part books. I've tested 5 books, all cut off early.
Thankfully, I saved the project files this time.
System info: ABB 1.1, OSX 10.5.7, QT 7.6 (1290), iTunes 8.1.1 (10), iPod Touch 2G with 2.2.1 firmware