Thorne, I'm clueless about c exceptions and model building but I can tell you today I got c exceptions 4 times doing the same thing-trying to turn off 'shadows' on Allie's hair (actually the P4 conformable curls I guess)--I finally gave up and tried moving lights. It seemed to do it particularly when I tried removing the shadows on the 'body'. I got away with it once on strand 1. This has happened to me before on this hair and since I know just enough about .cr2's to make me dangerous (LOL), then might there be a connection? BTW, mine does it at rendering also. Diane B