I am using an 80gb video iPod.
Just about every audiobook I have (there are several and I think it's more like all of them but I can't be sure) does this...
If the iPod has been off for a while, and I go to listen to an audiobook (it picks up from where I left off), it will play for a minute or so and then exit out and advance to the next audiobook. If I go back to the previous one (the one I was listening too), my place in the audiobook is lost (and set back to 0). Once this happens once, it doesn't happen again - until I stop listening long enough for the iPod to turn off. This happens about 99% of the time - no exageration. I feel like it's more like 100% of the time but I'd hate to be made a liar at some point. ;-)
Sometimes I can fool it. I might stop and start it every 5-10 seconds for the first half minute of play or so when I pick it up and it will be fine (but not always).
I did a reset/restore on the iPod to no avail. The firmware is at the latest as well.
Has anyone else experienced this?