How do I stop the GUI from flickering on a new scene?

I have a fairly complex scene and a fairly complex gui. When I begin a new scene (after pre-loading it with loadlevelasync), I see a brief flash of the scene with no gui before the gui is drawn. There are some other weirdnesses in the flash. It looks almost like a negative. I think its missing some post effects or something. Even weirder I've tried using a screen capture utility to grab a movie that demonstrates the problem, and the screen capture never captures the flash. I'm using unity 4.2 on OSX lion. It seems to happen both in an editor and when built.

Any ideas how to fix this?