Hi,

First check whether your card is 'locked'. There is a small lock with with your card. If it does not work, you better check with another memory card (if you don't have anymore, borrow from your friend). If this works, then the problem is with the card, and this is the most probable cause. It happens sometimes. If it still doesn't work, the fault is with the camera, Take it to a authorized repair shop.

Hope i helped!!