I’m having problems running the previewer in my…

I’m having problems running the previewer in my sandbox. I pointed wp-themes.com to my IP in the hosts file, and it directs there, but all I get is an instant whitescreen. Switching the hosts file on and off lets me see the real previewer vs. my broken whitescreen. I have not made any changes to the previewer code yet.

Anybody have any idea of what kind of voodoo black magic I’m missing?