Why?: All of a sudden, when importing NEF files, the "raw format is not supported". 'Been doing it successfully for months the same way: inserting the card into reader.

All of a sudden, when I try to import NEF files from my Nikon D5300, the "raw format is not supported".

I've been doing it successfully for months the same way, same card, same camera, same windows machine: inserting the card into reader.
I am using Lightroom 4.4; camera raw 7.4

The only thing different is that during the  past 2 weeks, I imported NEF files from that same card to my iPad with the Apple brand SD card reader.  (was away from home and my windows machine).  Could this have changed something on the card?
Thank you for your help.