The all do and none of them provides stellar performance. The default is really slow and it can be sped up a bit by playing with the settings. Too much speeding up though really compromises the quality of the noise. The link for the latest/greatest et cetera is
http://www.softick.com/bluetooth-audio/.
First, back up the device. If the card can be read with a card reader, then copy the files to your computer before formatting the card with the "quick format" option and after formatting it, check it out in the device and if that is good, then start adding files back to the card. If the card is readable by the card reader, then COPY all of those files to your desktop before proceeding.
Next, execute a hard reset with the card installed and see what happens. There is a good chance the card will be visible after a hard reset. If you do choose to format the card and it is readable, copy the entire card to your computer.
In the for what it is worth game, all of the brands occasionally have problems. I have found Sandisk to be a bit more reliable.