Hmm, for me with maya 2008, if I use the hardware renderer with motion blur turned on, it will always do a complete run up, regardless of whether or not I cache my particles.

Bummer.

I don't think I can use mental ray because it doesn't seem to be able to use the per particle rgb attribute. It uses an actual shader and I need to to use the PP attribute.

I guess I was hoping someone would know of a switch somewhere that would turn off the runup.

Thanks anyway.