When I booted up my 1 gHZ 17" iMac this morning, my screen had gone to "negative". No more Aqua! It now looks like a photo negative, with no color. I've run DiskWarrior, and I've run Norton Anti-Virus to see if I could find the problem. I've also tried to find a way to reverse this in my System Preferences. Still no luck. I'll bet this is something that I should know about, and the it is very simple to repair. Will someone help me? Thanks!