Hello, I would check if the card has a physical lock on it that slides back and forth on the card. If this doesn't work you can try to format the card with your computer.
1. Insert card to computer via card slot or card reader.
2. Locate it using the "my computer" icon or "computer" from startup menu depending on operating system. xp,vista,windows7 etc.
3.right click on card icon and select "format" option
4.After this is completed try to format in camera
5.If this still doesn't work make sure memory slot in camera is clean debri could cause reading errors.
6. If possisble try using a different card to see if it works. Do this to try to isolate the problem
Hope this helps