Graphics Scaling issue in SL

[rossipoo]

This doesn't happen very often, but I have noticed a graphics issue that seems to be related to scaling; I believe that it first started after I installed Snow Leopard, and it appears in Preview and Aperture. In Aperture it may happen after a crop, if the application is restarted, it goes away. In Preview it happens after an image is resized (the pixel size, not zooming), but before it is saved. I don't really use iPhoto so I know about it. It's hard to describe so I have attached a screen shot. It also happens the same except green, I have never seen blue.

I have a Core Duo iMac with the x1600 Radeon. Does anyone know what this is, or how to get rid of it?