I have fought about this as well. Because the system continues to run. However the screen doesnt update anymore at all. It might also be related with the usage of shaders, altough while i have the editor active (it’s a small start for a scene editor im working on) i have set render.setShaderOff(10000). But i dont know how much gets disabled when doing that.
It’s actually a macbook pro 2.0GHz with a ATI x1600 256MB. (just for reference is somebody experiences the same)