Lathe object artifacting

I am creating a custom lathe object by creating a circle, converting it to a lathe object then reducing the build angles to create a sort of 1/4 doughnut shape, All works fine apart from the ends of the custom lathe shape have huge 'spikes' extruding from them.
Any ideas?

I'm having a similar issue myself... I have a simple outline created in illustrator and converted to a lathe object in ProAnimator... a pan. It looks great when the build angle is a complete 360, however when I change it to just make a pie shaped piece of my object (or remove a pie-shaped slice of the object), I get these crazy artifacts on the ends. I have tried a couple changes with the path in the illustrator file, however it has only given me a different artifact, not eliminated it. Any ideas??