Hello. I have a 5 year old PowerPC G5 running Mac OS X version 10.4.11. It's just developed this weird glitch. The desktop icons, menu bar and cursor are surrounded by squares of dots in a grid pattern. I've uploaded a snapshot of it. Neither restarting, nor shutting down and restarting have had any effect. Has anyone else had this problem? If so, is there something I can do to fix it?