To reproduce:
1. Create a new project
2. Build for Windows Phone 8
3. Notice that the editor stopped redrawing. Any newly opened windows appear white and if you try to resize the game/scene view the editor will freeze completely

Sometimes you can see that lightmapping is doing something (bottom right corner, usually "Solving runtime") and after a moment the editor crashes with no bug reporter (due to RenderTexture.Create failed: cubemap not supported)

This is related to our new lightmapping system, as reducing the default scene to it's old format (no lightmapping, no lights and no skybox) solves the problem.

Regression since 5.0.0b5