Jim this is what i found out so far. I am sure that you already know how to format you card but here it is again, don't mean to insult you but just in case. Place it in the camera.
There are 2 buttons on the D70 that say "Format".
They are both in red.
One on the top right button of the camera and the other is to the leftof the viewfinder.
Press them at the same time for 3 seconds.
The lcd will blink "For".
Press the 2 buttons again. This should be it. http://www.ehow.com/how_5125786_format-m... Now I do know that if the green light by close to the the memory card slot blink you have a BGLOD (blinking green light of death) and apparently Nikon will still fix these even if your camera is out of warranty :) Also, you are using the Nikon approved media card only? Just to make sure because this camera is finicky about it. I would try and take your media card and place it in the media card slot of your computer (hope you are using one, sorry for the assumption) and see what it shows up as. Take one of those cards and format it with your computer and see if that makes a difference.As you know I am sure, all data on your card will be erased, so be careful that you do not lose anything of importance. Also make sure that you format it as FAT not FAT32 or anything else. If it formats well in the computer and works in your camera, you know that it is not the card. Give this a try and see if it makes a difference. The manual I used is on http://www.kenrockwell.com/nikon/d70/d70... and this is a great source of info for people that have issues with the format http://www.tomshardware.com/forum/36652-... Good luck and I hope this will work for you.
The pins of card holder get loosen and disconnected by a certain time using CF, and some time your card it self get damaged when you use a defective external card reader which may be a cheaper quality,and remember when you insert a damage card in your working camera, it immediate broke or bends the pins of your camera's card holder. and the Result "CHA / For"