Sounds like the screen refresh rate has been changed to something, incompatable with the monitor.
Go into Safe Mode.How to start Windows in Safe Mode
Control Panel / Appearance and Themes / Display / Settings
tab / Advanced
button / Monitor
Set the Screen refresh rate:
Apply / OK
Reboot, and see if that works.
Or, see if this helps:WARNING:
This is a registry edit. If you're not comfortable with working in the registry, DO NOT ATTEMPT
Improper changes to the registry could render your computer inoperable.Remember to backup the registry before making any changes.
Instructions, on how to do that, can be found here:How to back up, edit, and restore the registry"Out of Frequency"