4GB Clip+ w/ 16GB microSD - 2 audiobooks not listed out of 36 books on SD card

Looks like the song limit, even though there were only 4,638 files on the microSD, was the problem. Deleted several audiobook folders from the microSD card and now the two missing audiobook folders show up. Frustrating to have space left on the microSD card for more content, yet cannot use it due to the Clip+ having some kind file limit (that varies).