Cheers guys.

Dave you would think that, but its not the case. I can introduce the artifacts simply by upping the noise frequency on the volume noise that is plugged into the blob map of the particle cloud. If I lower it they go away.

It must be something with the noise and the mental ray.

Murambi - Have a quadro 2700 in my laptop, a quadro 1700 (I think) in my workstation at work and an ATI 3850 at home. And if I am honest I see virtually no difference with any of them unless the scene gets really heavy in the viewport then the rank would be 1. 2700, 2. ATI, 3. 1700.

Steve