As with my other post here a few minutes ago, this bug disappeared until the last patch yesterday that udpated our game updater. I was able to have the fullscreen (windowed) mode on and alt-tab to another program on my computer and then come back to the game with no problems. Now, it just shows me a black screen when I do. Using regular fullscreen fixes the problem, but gives me the load time wait each time and I can't keep an eye on my game on a separate monitor.