It has happened every single time that I've done this, if the game is open and you stay inactive enough for the windows timer to turn off your screen, when you return and the computer turns on the screen again, the game does freaky stuff while in black screen, freezing the whole computer, not being able to alt+tab, open the task manager or close the game.
I think it should be easy to achieve the error, but notice that I play the game from an external drive connected by usb. This drive is password protected, but once you open it, it remains connected, it should not be like access is forbiden because I can access it and open any other program after the screen turns on again in any other situation).
To repeat it just open the game on steam (all in the external drive) and just leave it there until the screen is turned off, wait for a couple minutes and then just move the mouse or smthg and everything has exploded, boom, black screen, freeze and all.
The only solution I found is restart the computer and is quite annoying
Memory 16Gb DDR3
Graphics card: Nvidia 840M
Processor: Intel i7 5500u
External drive: WD passport 1TB