I have a Nikon D70 and one day my camera said "the card could not be used" and I put the CF card into another dslr and it worked perfectly fine on that one. I only had five pictures on that card if that matters. Then I bought a brand new CF card and the camera said it needed to be formatted, so I formatted it on the camera but it still said the card could not be used. I'm thinking since it's an older nikon model that the camera is the problem, but I've had it for a while and had no problems before at all.