I'm running 10.5.2 on a 2GHz C2D BlackBook. Recently I've encountered 3 symptoms that suggests Quartz Extreme stops working after the computer's been running for a while (and by a while, I mean it could only be a couple hours). I've recently (a few days ago) set my desktop picture to change every minute. It's supposed to fade smoothly between pictures, and it did for a while, but then eventually I noticed the fading transition had stopped and the pictures were just switching without any kind of transition. The problem was resolved after a restart. I don't use iMovie often. But I opened iMovie '08 yesterday and I got the following error message: "iMovie requires a graphics card that is compatible with Quartz Extreme. One or more of your graphics cards does not support Quartz Extreme." My only option was to quit iMovie. I noticed my desktop picture was also not doing the transitions any more. After a restart, both problems were resolved. Today, I got the same error message in iMovie and the desktop isn't transitioning again. I haven't restarted yet, but I assume it will fix itself when I do. Also, I tried adding a widget to my dashboard to see if I get the ripple effect, to test my theory that Quartz Extreme (or is it core image, or core graphics?) stops working after a while. I did not get the ripple effect I usually get when adding a widget. Since I just started using the changing desktop feature and 10.5.2 is a new update, I don't know if one of those could be causing the issue. I'll try turning off the desktop transitions and see if it continues. Anyone else with this issue? Or know how to resolve it? Thanks.