This is driving my a little crazy. First, specs: Macbook Pro 17", 5,2 (late 2009) 2.8ghz Video: 9400M, 9600M GT 512 ram 4gigs ram 500gig 7200rpm drive Snow Leopard is fully updated. Photoshop CS4 is just pegging one of the core's on the CPU, even when doing nothing. And, any changes I make like moving a layer, editing some typing, transforming something, it doesn't show up until I do something like zoom in or out, or change the screen mode. It's sort of not usable, since I can't see any changes I make without doing something to change the screen. This seems to all be started today, I don't recall these problems before. I ran a permission repair and a verify disk.