I know this reply is too late. But i believe this may help someone in the future.
The same thing happened to me yesterday. I was in the middle of a short film shoot and my camera started giving me "Card write protected" message. I searched in the forums and found that it's the problem with the card reader inside the camera.
I was left out with no other options at that time, so '''i tried cleaning the camera's memory card compartment by wrapping cloth at the tip of a small knife'''. And when i turned on the camera, it got worked like magic. :) Give it a try before spending some bucks on servicing it.
Hope this helps.