I have all of my DW audiobooks on my car Ipod, which is connected to my car radio. Short story is that sometimes when I'm in the "audiobooks folder" and press the "next" button on my car radio (which, when in Ipod listening zone, would normally advance to the next song on a playlist or randomly bring up another song in "shuffle" mode), it will move forward to a different audiobook file in the current order they're stored--but will not always land on the same place!
For example, yesterday, I was listening to the end of Part 2 of "Making Money." I accidentally hit the forward button, and it went halfway through "Part 1" of Jingo. I hit "back" and it started a quarter of the way into Part 2 of "Making Money." I hit "back" again and it went three quarters of the way into "Hogfather" I hit forward and it went to the beginning of Part 2 of "Making Money." Now, keep in mind I had totally finished all of these files, so there should have been no "memory" effect. This doesn't happen when I use the iPod normally, because the Ipod itself makes you choose a chapter unless you hit "Resume." Some weird thing with the car stereo iPod interface. Anyway, it does make a bit of an entertaining (and randomized) listening experience.