Since mid August my 24" Alu 2.8 exterme iMac has been flawless. Last night I just installed Quicktime 7.3, IMac Update 1.2.1, and iTunes update 7.5. Right after the restart I noticed dancing pixels on my screen. Spordic but frequent clusters of white pixels marching and whizzing across the screen horizontally. Especially bad in Safari with this animated GIF banners. Has anyone else noticed this?