I have never seen that, but then again I don’t really use particle world.
Just as a matter of interest what happens if you up the colour depth? I assume your working in 8bit?
Depending how it looks in motion, what you are seeing could be described as clipping.
If you can provide a download for your file or an explanation of how to recreate it I would be happy to see if it does it to me.
Oh just one thing, make sure you are using “Adaptive resolution – Open GL off” in the fast preview window. I have never seen anything I like with open GL being on.