According Thomas Knoll in the Adobe forums, Nikon encrypts the white balence data on its D2x and D2Hs camera’s:
“No, Nikon has never disclosed proprietary NEF data to Adobe. However, Nikon made a significant change with the Nikon D2X and D2Hs cameras. They decided to ENCRYPT the white balance data inside the NEF file for these cameras. Previously, the white balance data was stored in non-encrypted format, and was readable to third party raw converters using simple reverse engineering of the file format.
… Adobe is still going to support the D2X in the upcoming Camera Raw 3.1 release. However, because of the white balance encryption, Camera Raw will not be able (unless Nikon backs down real soon) to read the “as shot” white balance from the camera, and users will be more likely to have to adjust the while balance manually in the Camera Raw dialog, since Camera Raw’s default white balance will not match the cameras default white balance.”
This is vendor lockin from Nikon which now forces people to use Nikon Capture. Even if Nikon Capture is not a very expensive package I can imagine Nikon should give people th eoption on which software they use to convert their NEFs. In the end it is the photographer which owns the digital image!