Yeah i had the same thing , i Downloaded a zombie version of singleplayer it ran Fine except that i couldnt play with my friend, So i bought the game from Steam just yesterday And it wasnt starting !! Well ill tell you what i did that worked 2 me , Run the game Then you get Black screen Wait for like 1 oe 2 min. Then press on the keyboard button to pop up the windows menu , After that Bring up the task manager But dont stop any programs, Try to lower the game (you know when you press the _ button for ex.) , This will be hard btw, After you done it Close Task manager And you will ear a Sound from the game , Pop the game up again wait like 30 secs if your pc sucks And there you go You are inside the game