Lightroom :: 4 Hangs When Importing Nikon Electronic File Format

I use Windows 7 Pro, 64 bit.  I saw an item that suggested going into Explorer and clicking "show hidden files and folders": I clicked that and then restarted the computer.  No change in behavior.
 
I've left the import up for more than 5 minutes (someone mentioned that LR4 is slow): I never got the import done. 
 
When I click the "X" at the end of the import thermometer, I get a message (in that location) that the import is canceled.  The display in the main window (where the image would appear) still says "importing files".  I have to quit LR4 and start it up again to do anything else.
 
I was previously using LR3.6, that used to work fine.  I tried going back to LR3.6 to import some files I recently shot: now LR3.6 does the same thing as LR4 (hangs when I try to import Nikon Electronic Format files).