Using DayZ Launcher from Steam, click play button down arrow "play without mods". Login screen is black where it would normally render the background and your character. You can still search for servers and click on play to join. Once in a game, screen is still black except for the UI. The only work around is to not play in 1080p. In other words, you cant play at max resolution. This problem does NOT present itself if you are playing WITH MODS. I've gone as far as uninstalling the mods, restarting and joining an official server and I still get the black screen at login and in the game until I lower the resolution.