Some mesh property makes fur unrenderable

[static244]

I made a pretty neat model (in maya 5.0) and now I want to add fur, however it will not render in the scene.
I did a little test:
-exported my model as polygons only, with the basic lambert shader only
-made a new scene, made a polygonal sphere, added a basic fur description
-the fur rendered fine
-imported the model and rendered again, the fur wouldn't render any more

This has happened to me before, whats the problem?

Thanks,
static244