I'm wondering what size your card is? When I first got my KN7 it came with a miserly 8mb Card and I had a similar message come up on the screen. On making enquiries with Technote as to why, I was told it was "FULL" and was advised to get another card with at least 256mb on it. I asked why the KN didn't come up with the message "Card FULL" but they couldn't tell me? Too simple for the 'boffins' I suspect.
Could be your answer though.
Regards
Audrey