http://www.nikonchat.com/focusing-screen-nikon/

Nikon D200 menu buttons are not working?
I just bought a Nikon D200 with a battery grip Jenis. For some reason, the camera will not focus or let me use the menu unless you hold down the button AE-L/AF-L for a few seconds and then release it, and then from March 10 seconds later freeze again. I entered slowly and changed the menu settings AE-L/AE-F hold down to use, and the focus began to work, but the menu buttons (the ones next to the display screen) still will not work unless you press the buttons for several seconds. Help?
Get it serviced at an authorized service center. This is a small problem and is easily cured. Even if you have to pay for the service, make done.
Nikon K3 focusing screen on K20D