Hi All,
I had a different problem with my D70 months ago, the symptoms were quite similar to those some of you described (such as inability to read CF-card, menu doesn't function etc). However, I realised that it was my own stupid mistake that resulted in this.
It all happened when I tried to slot in my CF card into the compartment whilst in the dark. When it didn't seem to slide in nicely, I insisted that I got it right and pushed it in with a slightly greater force. This caused two of the many pins in the compartment to bend and touch. When I got home and managed to get decent light, I saw that two of the pins were now entering the same pin-hole in the camera, even when I slot the CF-card in the correct way!
Anyway, I brought it back to Nikon and they repaired it.
I suppose the problems most of you are encountering are of a different sort, but for those who are as careless as I was, do shine a light in to check. Just to rule out this possibility.