Dang. Still there, eh? I was hoping Carrara5 had cleared it up. I wasted several hours with a light-lab confirming that this was a problem in the GI render. Basically, it can't deal with "short" distances between the transparent object and the object being shadowed by it. (In my light-lab test of Carrara4, "short" is defined as "six inches Carrara scale." However, scaling the scene did not seem to take care of the problem either.) Best answer I've come up with for Poser renders is to add direct light on the figure's face. A nasty compromise, but...