I'm still trying to figure out what causes the crashes too. sometimes it all renders out fine, but more often it crashes after 1-3 frames. I've read it's caused by animating the focal distance, but it seems that's not the only cause. Currently I just restart C4D and try it again until I get it to work. I've had most success using the render queue rather than the picture viewer but it may just be coincidence...
In fact an animation that crashed last night after 1 frame, I re-opening and started re-rendering again today. Without making any changes whatsoever to the file it seems to be rendering out without any issues, so I guess maybe there's no real "cause"