Help nov 7 advanced losing music and viceos

[mergatroid]

Hi

I have an ainol novo 7 advanced and it often comes up with an error saying that there are no files loaded on the sd card, either internal 8gb or external 32gb card.
When I connect it to the pc I can see all the files but still the novo 7 advanced does not see them.
If I move them to another directory on the card the aino 7 advanced sees them again for a few days before the whole process happens again.
Any ideas as it is really annoying?

Cheers

Mergatroid