From Nikon Europe:
How to avoid RAW file support problems with Nikon software
When RAW images captured with a Nikon digital SLR camera are transferred to a computer, viewed, or edited with an earlier version of Nikon software that does not support RAW images captured with the camera used, some RAW image data may be corrupted and handled incorrectly by the software.
To transfer RAW images captured with a Nikon digital SLR camera to a computer, view the images, or edit them with Nikon software, please be sure that you are using the latest version of that software.
For example, if you are using a version of ViewNX (Ver. 1.x) or Nikon Transfer (Ver. 1.x) that does not support RAW images captured with your camera, please uninstall the software. To transfer image data, use the most recent version of Nikon Transfer 2 (included with ViewNX 2) that supports RAW images captured with your camera.
Use the CD containing Nikon software that supports RAW images captured with your camera supplied with purchase of your camera to install the software, or you may download the latest version of software compatible with your camera from this website and install it on your computer.