As a teacher I use a projector all day long. After upgrading from 10.6.2 to 10.6.3 last night without incident I was surprised to find out in class today that the screen on my MacBook scrambles when I attach the projector and go into slideshow mode in PowerPoint. Exiting slideshow doesn't fix it. Unplugging the projector does. I soon discovered that it's not limited to slideshows. My screensaver triggers it too. So does going full screen in Quicktime Player. Basically anything going full screen when the projector is plugged in does it. I just tried it at home expecting the same results, but my external monitor doesn't trigger it. Hmmm, I'm using a DVI connection to the monitor whereas the projector is VGA. Does that sound like a driver issue? If so, why is the picture just fine on the external display, but the internal screen is messed up? I don't understand. I see others are having display issues too. Has anyone found the answer?