Never had this, but somethig serious is happening.
You said that you still have the photos on the canera's card.
Try to open them with any type of viewer and see if the photos are not corrupted already on the camera's card. I have that on one of my cameras just due to a bad card... and nothing else.
Please note that NX2 stopped being upgraded and newer cameras are not supported.
If they are ok, make some copies to the hard disk in different locations.
Do tottally clean the previously NX2 instalation, not only putting it on trash, use appdelete or similar apllication and reinstall.
Open the files in one of the locations and see.
Still happening? Forget NX2, and use something else