Do ensure the card isn't locked or the slider on the side isn't 'stuck halfway', try flicking it a couple of times. Then with a non fluff-free cloth gently wipe the gold contact strips... all you can do is try again ensuring that you format it first.
If this doesn't work then the only option is to try another card. You really don't wanna be turning things OFF and ON to get them to work.
Should it be a new card then see if you can exchange it, some case you *may* have to send it back to the manufacturer.
It could be the camera, there's only one way to find out and that is by trying another card... even a borrowed one. Just thought of another option..... try it on a card reader, some computers have them and some don't, in this case you use an external card reader
Dave
