Is the card locked or broken?
I was given an SD Card with some lovely styles on it which play perfectly but when I 'tweaked' one of the styles and tried to save my new sets, I received a message saying the card is 'locked'
In actual fact, it isn't, but the little lever that would normally operate the locking/unlocking action is missing, hence I can only play what's on the card.
Just a thought.
Audrey