It might be the way you are downloading them. I believe that Nikon Transfer has been updated to overcome a corruption bug which affects Adobe products.
If you are using Nikon Transfer, it might be worth updating to the latest version, and downloading your photos again. Or use Adobe Photodownloader instead (I would).
Also, accepted wisdom is to download photos off the memory card using a card reader, rather than via the camera USB, as it is less prone to problems. YMMV.