Edit: I worded this badly so I'll try again: When I add a light to the scene, then switch it off, and render, the render is un-lit. If I then check 'illuminate with default lights' in the viewport, it doesn't render using the default lights again. The only way I can get to render using the default lights, is to delete any…
This turns the light on/off when rendered. Is there a way to turn a layer of lights on/off other than switching each light on/off individually? This would allow me to toggle between scene lights and the 'fake' default lights in the viewport with a single click.
Defaults lights only render when there are no lights in the scene, as kind of a backup for no lights. Once you make lights, you can override them with the default lighting, but only for the viewport. I think the intention is to give you easy-to-see viewport illumination when your actual lighting can't be represented…
You can use layers to switch sets of lights on and off by turning them to renderable or not. (properties by layer). Then you could have one layer with a light positioned near your camera and linked to it in order to simulate the default light.
It would be nice if scene states supported the existence or not of lights. but just select them all and delete them if you like OOOOOR have them as a reference file ;)
Sounds like an easy job to do with Maxscript... a one-click light switcher. I bet there's something already made for this, or very close (and easy to edit into shape). http://www.scriptspot.com/
I think the keyboard shortcut is Ctrl-L to revert the viewport back to the default lighting. It might be the same as what you're trying now, I'm not sure but Ctrl-L works for me.