audiobook tracks not playing successively

I listen to audiobooks on my iPod all the time. As of a few days ago, they stopped playing continuously. After each track it stops instead of moving onto the next track automatically. While it's playing, if I press the >>| button, it doesn't skip to the next track like it would if I were playing a song, it goes to the menu and I have to manually scroll to the next track and press play.

I've done everything I can think of from changing the repeat and shuffle settings in the iPod to changing all the info for the tracks (adding disc numbers, genre - books & spoken, ticking the gapless album, skip when shuffling and remember playback position boxes). Double and triple checking they are all labeled Audiobook, not Music. Artist and Album name are all filled in.

I've never had this problem before. The only thing I can think of is that the other day, the iPod froze on the "connected" screen while it was charging attached to my computer. I googled to find out what to do, reset it and it's been fine since. I don't know if that's related or not. Is there something really obvious I'm missing?

I have a 3rd Gen iPod Nano.

I'm not sure if this is relevant, but iTunes doesn't seem to want anything called an Audiobook. I added new files to the library, and reclassified the tracks as Audiobooks. They disappeared from the Music Library and reappeared in the Audiobooks Library. Then I clicked Get Info > Options and see that the menu where you choose Music, Movie, Audiobook, TV show, Music Video, was reset back to Music. I fixed it then dragged the files to my iPod, clicked Get Info > Options and again that menu was set back to Music. I fixed it again and it seemed to stay, for this session at least.

Am an avid audiobook listener here also. Where are you getting the audio books and what file format are the ones you're having a problem with?