I believe this bug requires to be fixed in the next upcoming patch, I have started my 16 th game and again it has had it. Before the update we are on now, I rarely had problems with it, it it is now every single game I play that I have to wait or leave due to the black screen.
It's a common bug on less powerful machines. In the lobby, that red/yellow/green light is the loading icon. If you wait for it to go all the way to green, the black screen is much less common. Most of the time the black screen goes away after a minute or two anyways.
Oviously it's need to be fixed, but for now try to use those workarounds: http://steamcommunity.com/app/233250/discussions/2/810938810899540110/ And post here if any of them help you/
