Audiobooks from Netlibrary won't play anymore

In the past I was successful in downloading and playing 2 audiobooks from Netlibrary’s media center to my clip. Yesterday, I tried to download another book, and it won’t play at all. When I select it on my clip and press the play button, all it does is scroll through all the chapter numbers, but it won’t stop on any one chapter and actually play anything. I deleted that audiobook and downloaded another one. I got the exact same result.

What is going on with my clip all of a sudden? Can this problem be fixed?

Thanks!

what program are you using to sync the files? i think net lirary files are protected so you will need to use an app like windows media player 11 to sync. 

I actually figured out my problem. I was attempting to listen to mp3 files instead of WMA files. When I transferred a book in WMA format, it worked just fine.