Today I encountered a problem when starting iMovie. A small dialog box appeared telling me that I need a graphic card which supports Quartz Extreme. After pressing the ok button iMovie shutdown. I never had this before, but after googling around a litte I found out that quite a bunch of people has this problem. It seems that OSX starting at version 10.5.2 got this problem when prior working with an additional external display or when the machine comes back from suspend mode. A simple logout and relogin does the thing as mentioned here but I would appreciate when Apple’s developer would fix this bug. There is enough information and hints on the web to pin down the bug. There is no need to reboot your machine as mentioned in some articles, after a new login quartz is coming up ok. I have not checked if there is allready a bug opened at apple for this.