Monitor going black

When I first open certain games the monitor will go black and the power light will be flashing and the screen will flicker, I am still able to hear the game in the background so its still running but the monitor just isn't showing it. I have to unplug the monitor and replug it in for anything to show up. This will also happen sometimes when im in the game and I go back to my desktop then try and go back into the game. I just got a new video card, motherboard, and psu and this was happening before and after I got the new stuff so im thinking its the monitor but im just trying to make sure before I plan on getting a new one.