http://kb.sandisk.com/app/answers/detail/a_id/1100/kw/audible%20books/r_id/101834
Here is a help to get Audibooks to work. I was looking for a solution too and my Audible Books would not show up until I went to My Computer, and went to the Sansa and moved the files from Audible to Audiobooks. I have not tried with Overdrive yet, but will at some point.
