I've created a cloth scene composed of nCloth objects, and have cached using single file per frame.
I've setup the scene for rendering with mental ray, and it always crashes with I try to render with motion blur. I haven't used Maya Software (I can't either, using mental ray shaders), but this problem is definately related to mental ray's motion blur...
My settings for motion blur are:
Motion Blur: Full
Motion Blur By: 1.000
Motion Steps: 1