Another possibility is that the normal of a polygon viewed from the camera becomes exactly 0,0,0 (a line), this normally doesn't happen, you are using floating point and always will give some small number even very small. But the probability to happen will increase with objects very far in the horizon and the computation can give a denormalised floating point value, a NaN or a normal exactly 0,0,0.
Poser in this case should have to do is not render this polygon or render it as a line, but if instead tries to render it as a polygons very strange things can happen and not only a crash.

Stupidity also evolves!