Before, I want to thank Epic for the upcoming awesome 4.2 update. t. I am using 4.2 preview version (compiled one from github). Sadly with it I am getting almost every old sample having black screen inside the viewport (except some old samples that did not update from 4.0.2 to 4.1 like Crad game and Effects cave). The actors are still visible but the entire scene is black (even with the new Stylised demo (which has a light brown contour but everything is black isnide and when you hit play, you get the cinematic working in colours). Also I am getting a teremendous FPS drop in the samples that still work (Cave demo used to run at 45+ FPS , now I am getting around 15 FPS). I think all your samples should be updated now that 4.2 is coming.
Stylised viewport (same for many otehr samples): http://i.imgur.com/DSUea8r.png?1