Hi,
we have a big problem with Unity Pro since version 4.2, and we encountered the same bug with 4.2.1 today. Basically when using the Camera Motion Blur full screen effects, if you select to exclude one or more layer the editor crashes all the time when you try to preview a scene.
We are only receiving an unhandled NULL exception in the editor log file and nothing else:
Receiving unhandled NULL exception
Launching bug reporter
Is someone experiencing the same problem? We’ll fill a bug report about it.