Unity crashes when viewing any material.

My Unity has started crashing when I view any material, including materials on models. Yesterday I worked around it by unplugging my second monitor, opening Unity up with a new scene, and resizing the window, then re-engaging the second monitor.

Today it crashes no matter how I manage the resolution. Not even on a single screen. What do?

Do you see any error messages before/when it crashes? How does it crash? Does the editor freeze/stop responding, or does it simply close?