Both my mac-minis developed the "Quartz Extreme not longer supported" problem. I started my project on one then switched to the other. Reinstalling the system fixed this problem for me. It's a tedious fix but I was on a deadline and none of the other "fixes" were working for me (like changing the display settings or restarting) Plus I ran out of computers to switch to. I was surprised that this problem goes back to early 2008 and Apple has yet to address it in any serious way. I did an exhaustive search and finally came across the re-install fix here. Thanks ifixit.com!