Int Poser 6 (I don't know about P7), I've got rid of this "feature" for specific props by switching to the "properties" tab of the Parameters dialogue and reducing the "Crease Angle" down to something like 20 degrees. The default is set too high IMHO. Turning smoothing off for an object doesn't alwayswork properly (at least, not for me - I'm probably doing something wrong) but changing the crease-angle sorted it for me, so I've never investigated fuirther..

Cheers,
Diolma