Particle system disappearing after being paused.

I have some particle systems which disappear after they have been paused (via ParticleSystem.Pause()).

They are typically shorter lifetime ones if that has anything to do w/it. We allow the camera to be moved around while paused so the player can marvel at the amazing fx, but some of the particle systems just stop rendering when paused (show back when unpaused). It doesn't seem to happen until the particle system has moved outside of the viewport, and then back into it.

Any ideas why?