The recently released NVIDIA GeForce Game Ready 616.56 graphics driver has pleased enthusiasts with its performance improvements in calculations and path tracing (but not in-game), but it also introduced an unpleasant bug for owners of standard color-depth monitors. Users have complained extensively about constant flickering of displays and periodic spontaneous changes in brightness. As discovered by the community, the issue only occurs on monitors running in 8-bit color depth mode.
If your monitor supports 10-bit color, just open the NVIDIA application, go to System > Display tab and force the mode to 10-bit. This instantly eliminates flickering. On some monitors, you may need to lower the screen refresh rate slightly to unlock 10-bit mode. If the monitor physically only supports 8-bit and does not allow 10-bit mode to be enabled, the only stable solution is to roll back to the previous version of the driver (branch 610.xx).
NVIDIA representatives have confirmed the issue and said they are currently testing a fix. Patches with fixes should be released soon in the form of extraordinary patched drivers.