[ODE] Bouncy sphere/trimesh collisions

[Brad]

I've got a sphere that collides with a trimesh at a fairly high velocity 
(though not high enough to make the sphere go through the trimesh or 
anything). I've got bounce set to 0. Sometimes when the sphere collides 
with the trimesh (which is a fixed, bodyless geometry) the sphere 
bounces up pretty high, and other times it works right and pretty much 
doesn't bounce at all. Is there something I'm doing wrong?