Last night I downloaded the 1.5.4 update to my G5 iMac. This morning when I turned my computer on all of the system graphics were messed up. I've tried restarting and reseting the PRAM. That didn't help. The weird black dots/lines appears over all icons, near the mouse, on the edge of windows/programs, all over the dock, and over other various things. I have no idea what to do to fix this. Any suggestions?