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/