I had the same problem a few days ago with my D70 (stuck on 335) and my computer would no longer recognize the 1gb Sandisk card either. Since I had a number of new images on the card I used "PC Inspector Smart Recovery (www.convar.com) to recover the images. Two years of old images had never been written over even though the card had been used often and reformatted regularly. I disposed of the 1gb card and used a recent 2gb Sandisk card and the camera functioned normally now.
"Great things are not done by impulse but by a series of small things brought together." Vincent Van Gogh