I have the same problem.
For me, I have an 8gb microsdhd card.
I have it almost full of mp3's, which will read fine from the card on my computer or when placed in a MotoQ; but Blackberry will not recognize all of the songs.
It is quite strange.
Did anyone find these, or any other MP3 player downloads to work better for the Blackberry?
Where were the songs that won't play purchased? If they are iTunes store purchases, they will not play on your BB, because of DRM. However, Apple is now selling DRM free music, and you can upgrade your library for a set cost based on the number of songs/albums purchased.