Does anyone have any idea what may be causing this? I imported an obj model of the V3 poser head into hex and tried to do a symmetrical face manipulation. With symmetry turned off it works fine. With symmetry turned on however it really screws up.

Well one of the issues could that the V3 head is not symmetrical as its so Hexagon is trying to guess what vertices to pull. Ringo

Yes. That is the issue. Hexagon is attempting to move things symmetrically but the model is not completely symmetrical. What I'd suggest doing is cutting the model in half (down the center) and duplicating with symmetry. Weld the two sides and then manipulate it. Of course if you are attempting to create morph targets for Poser :) then this wouldn't work well for you:)