Nikon D50 CHR notification?

I have a Nikon D50 which i have not used recently but I charged the batteries and when I tried to use it I keep getting a " CHR " notification in the lower right corner of the top display and in the view finder and the camera will not shoot. The auto focus engages and everything works. I tried my battery from my D90 but same issue occurred. Any advice?

On page 125 of your user manual, CHR is telling you that the memory card can't be used.

Have you ever formatted that card? First when you first started using it and then at the end of each shooting day after successfully copying all your images to your computer?

What happens when you use one of your other cards?

Is the card greater than 2 GB? If so, it is SDHC, not SD. The Nikon D50 does not work with the SDHC cards.