I'm putting this here as a reminder to myself and in case it helps anyone else.
I have an NVidia GTX660 (latest driver) and an ASUS pb278Q connected via the display port. I have the power settings to turn off the monitor after 30 minutes and mostly leave the machine turned on. However, often when I come back to the machine and hit a key on the keyboard or wiggle the mouse the machine wakes up but my screen is blank.
I've tried loads of possible solutions and the only one that seems to work for me is to disable DDC/CI in the monitor settings from the menu. I believe this setting allows the computer and screen to communicate state changes or orientation changes. Now I can even turn off the monitor manually and so long as I turn it on again before waking the computer up my screen display is restored.