Go on google and search for 'crimson causing black screen games' or similar to read up on the problem Im not sure if the power efficiency toggle is supported with the HD7900 series cards but your issue sounds similar to others in that the core frequency of the GPU is dropping to low on certain games causing a black screen, which is due to the new power efficiency service built into Crimson.

In crimson go on Gaming>Global settings and see if you can see 'Power efficiency' toggle, If its visible try setting it to 'off'

If you need more information just ask, I'm not the best at explaining these things. Also, it seems when this issues happens in Civ V my PC completely crashes and I have to hard reset. There are some others but no point in listing them all I don't think. These are Mad Max, ArmA 3, Company of Heroes 2 and Mount and Blade. There are some games that for some reason this issue just doesn't exist. I have 3 monitors connected and my TV, I have tried without my TV connected, and just a single monitor. I have tried re-installing the games, and validating files but it's clear it's a problem with my PC not the installation of the games or Steam. I then re-installed drivers completely, but again that never solved it. I was on the latest AMD Beta drivers, so I reverted back to the older ones as I knew everything worked then, but that didn't solve it. I can fix that problem by going into Windowed mode, but for the other games I just can't play them as all I see is a black screen. In some games I don't get a black screen just the stutter, and I only get around 5-8 FPS. I noticed while I have this black screen that my Lighting on my Keyboard (Corsair K70) starts stuttering, and my mouse (Razer Mamba Tournament Edition) while I can move it, is also stuttering. So coming off another issue I had a little while back, I now have a brand new problem when I launch games in fullscreen my PC just shows me a black screen.

Company of heroes black screen