I just bought the Ambling Pro Edition for use on my Archos 70 tablet. I had a couple of mp3 library books that I transferred from my SD card into Ambling. When I tried to play the books, the screen shows "File Not Playable". At the top of the screen I get a message that the file is playing, but there's no sound and the progress bar at the bottom of the screen doesn't move.

I'm hoping someone can help me to understand what I'm doing wrong. Thanks.