Particle system disappears from object when key framed

#1

Hi,

  I have a cloud particle system that emits its particles on a square object.  The cloud is there and all but when I key frame the square or link it to some other object the cloud disappears.  I need this cloud to be in a moving train car but the particle system seems to be to picky.  How do I keep the cloud particles on the Cyan square?

Thanks,

#2

I just relized that the reason it looked liked it disappeared is bcause they got left behind at frame 0. And in the Position Object operator I had to click on the lock emitter box.