This problem has occured a few times now - Cinema4D crashes when I enter the Arnold Network Editor. It only happens occasionally, not very often, but it bugs me because it crashes C4D completely and harshly without saving any bugreport save. It doesn't freeze, it just crashes and closes from one second to the next.
I don't know if my setup/layout/habits may be responsible for this: I have the network editor docked in the same window as the viewport, so changing to the editor switches from my viewport panel. I also tend to open the network editor by middlemouse clicking the material in the material manager. I have the feeling that the crashes occur more frequently when I use the middle mouse method.