The raw data in the image files is corrupted, and the other viewers that don't show the corruption are merely showing you the camera-embedded thumbnail or preview JPG, not actually interpreting the raw data like LR is. If you open the images in other raw converter software, like the free RawTherapee you'll likely also see corruption although it may manifest differently depending on what the raw converter does when it doesn't have data:
http://rawtherapee.com/downloads
Sometimes the data becomes corrupted mid-transfer due to a poorly connected cable or poorly inserted card and retransferring it will correct the problem, but you've done that, already, and the images are still corrupted the same way. That suggests the data is bad on the camera memory card.
It is likely the card that is deteriorating so probably time to throw it away, or at least try another for a while to see if there are any problems with it, as well. If there are, maybe the camera is actually having a problem writing the photo data to the card, rather than the card not retaining the information as is normally the case.
If the images are very important and you feel like hacking a bit, you can probably extract the camera-embedded JPG preview out of the NEF using special software and use that JPG instead of the NEF, although it may be smaller dimensions and have less headroom for editing highlights and shadows.
The software I use to extract previews from Nikon NEFs would be EXIFTOOLGUI that works in conjunction with EXIFTOOL, both available from:
http://u88.n24.queensu.ca/exiftool/fo...
