Do you have the preview render set to opengl with scene lights? Using light maps and scene lights is better. Even with sw renderer there is an option for scene lights that is not selected by default. The only part that gets saved to prefs is whether to use OGL or SW. All the other settings do not get saved to prefs, but will be saved with file. So they have to be set everytime. C5 needs a bit better prefs config management.

No need to think outside the box....
    Just make it invisible.