This is a hardware issue, most likely. Try a different card. If that doesn't solve the problem then it could be a hard drive that is failing, or a bad cable if you are connecting your camera to the computer, or a bad card reader.
Hopefully you still have the memory chip with the images on it. If so plug in memory chip and try coping images directly thru your Operating system as compared to thru import thru Lightroom. Let me know if your still see this issue? Also when chip is in camera, do you see this issue on the preview screen of the camera?