Hello. Using Maya 8.5 on Precision 690, OS: XP-Pro, 2 Gigs RAM

I am doing a tutorial from the book, "Mastering Maya 8.5". I am on chapter 14.

I have gotten to a point where my render should be close to finished, but suddenly the light is rendering very strangely, creating a weird, crushed glass like texture wherever it hits anything. The rest of the low rez scene is looking fine.

I have attached a screen shot showing the problem. can anyone look at this image and tell me where the problem is?

I have gone over the tutorial steps and also played with various settings for the whole scene to try to sort it out.

Thanks, T