Sorry to hear about the memory card problem.
I'm wondering if you've tried a new memory card. That would give you an good indication of whether the problem is with the card or the camera. If you have a friend with a memory card reader that accepts your memory card type, see if the photos transfer correctly to his or her computer.
If you're using a memory card reader, try transferring the images with the USB cord that came with the camera. Also try uninstalling and resinstalling and/or updating the driver and software for the reader
If the card is the problem, format it (though not until you contact tech support as suggested below). You may still be able to recover the lost images, though there is no guarantee. We have some information about the photo recovery process here:
http://www.digicamhelp.com/processing-photos/photo-recovery/recovery-and-rescue/Do consider calling the memory card or Nikon tech support. They may be able to give you very specific help to solve the problem and tell you how to recover the lost images if possible.
Hope it works out for you. Let us know if you find a solution.