I have a scene that I’m using in Blender 2.78c. The scene sun lamps is not working. I made the scene with a previous version of Blender.
Oddly, environment lighting works and also lamps that was originally created. Lights that I add doesn’t work. I even tried importing the meshes to a new file with the same problem.
Disable (or delete) the Bevel modifier on the object “impulseengine.001”, then the lights start to work - don’t ask me why. Since I don’t get what that bevel modifier is supposed to do anyway, I guess it’s a negligible price to pay.