Screen turns black

Hey!
I’m working on a project with a friend. When I press P to start the game it works fine but on his computer the screen just turns black. Same thing with another friend that I sent the project to as an EXE.
What could be the problem?
//Evert

might be the mist settings, try turning them off …

you might not be able to see the mist because of your graphics card, wherer the other computers can.