Initial troubleshooting steps:
1. Uncheck the option Preferences > Performance > Use Graphics Processor.
2. If you're on Windows, update your graphics driver directly from the manufacturer's Web site: Adobe Lightroom GPU Troubleshooting and FAQ
3. Test if the display profile is incompatible or corrupt: http://www.lightroomqueen.com/articles-page/how-do-i-change-my-monitor-profile-to-check-wh ether-its-corrupted/
4. Copy here the first ten lines of the menu command Help > System Info.
Thank you!!!! it worked!
Good. To help others, which step solved the problem?