Lighting effects - working then stopped

I was working with three lights on a layer - everything was fine, preview was showing up, everything worked. Then suddenly the effect just disappeared. Not the panel, just the effect on the image. The three little light icon are still in the effect panel, they are all ON.

I have tried restarting, turning on/off Graphics processor, tried removing the lights.

When I quit/shut down etc and then reopen, the effects panel still shows the lights to be there, but they are not actually showing up in the image.

Help!