Render, viewport "Rendered" preview, and material preview white I've been working on a scene for a while now with no issues. Today, I found that when I rendered the scene, it came out as completely white. Furthermore, the material preview window is also showing completely white.

I've noticed that, until a few samples have been calculated, you can actually see some of the scene/material in the previews, but after just a few samples, the scene goes completely white. Here's a screenshot I managed to take of this phenomenon. 



And a screenshot of the material preview, which behaves similarly.



I've checked everything I know to check (which honestly isn't very much) and can't seem to figure out what's up. I've uploaded a copy of my scene (with most of the models removed) to demonstrate the problem here: https://blend-exchange.giantcowfilms.com/b/4535/
Your scene is simply too bright. If you lower the exposure to -10 in the Scene panel, you can start to see the color of the surfaces.

A more permanant fix is to lower the energy intensity of your 2 lamps in the scene, as well as the world HDR map.