Disable GPU acceleration. This is something Adobe really has to sort out quickly
You need to disable the GPU acceleration by going to Edit> Preferences> Performance > uncheck the GPU box and restart lightroom.
And do update your graphic card drivers as well as you said it was working fine earlier and once you update them you can check that box again.
Please let us know it helps.
Telling people to upgrade the driver is NOT the answer to this problem, which has been going on since April! The problem is exacerbated by driver updates and is now a major problem because Windows 10 automatically updates drivers. Adobe needs to get this fixed!