"Try three or four mil figures, with clothes/hair/background props/buildings/etc......... " 9 mil figures with clothes, shoes, hair & a number of props and still no crash for me and renders just fine. So I do think you have to push it further then that perhaps to see the bug. I've tried 12 mixed mil figures all textures, clothed and haired and still rendered fine.... But that was the max I could do, adding one more figure or prop would result in the render bug. Perhaps when the bug will show is also machine related, I've always got very little running in the background.

Artwork and 3DToons items, create the perfect place for you toon and other figures!

http://www.renderosity.com/mod/bcs/index.php?vendor=23722

Due to the childish TOS changes, I'm not allowed to link to my other products outside of Rendo anymore :(

Food for thought.....
https://www.youtube.com/watch?v=pYZw0dfLmLk