Please follow the below steps.
> Launch Lightroom
> Click on Lightroom > Preferences (In Mac)
Edit > Preferences (In Windows)
> Click on Performance Tab
> Uncheck the option Use Display Processor
> Relaunch Lightroom and check for the issue.
Let me know if this helps.
It's still the same.
What operating system do you use? (Windows or Mac)
Have you updated Lightroom to 6.3?
Check to make sure your card reader is not malfunctioning. Try to import using different hardware.