Digital Camera - Q & A

Very difficult to tell anything about your problem because of your lack of information.

There could be other reasons, the card has failed is one of them.

The reason for failure could be you were using it as a storage device and cards aren't designed for this. My advice is after every shoot, upload to your system then format the card in the camera.
This will keep the card "healthy" and working correctly for some time.

If formatting doesn't do the trick for your card you should replace it.