Is is starting to hit an object that has heavy transparency on it? I notice this happening in the scene that I'm working on right now. It screams along until the 3rd or 4th pass through and then it screams through the top 1/2 of the screen and then appears to freeze. I noticed that it's at the first row that has a pixel for the tranparent/reflective texture on a crystal vase. Once past the vase, it screams along until it hits the next vase. Go figure. John