Apple released iMovie 9.0.8 for the Mac on Wednesday with a fix that improves stability when using third-party QuickTime plug-ins. Some users have been experiencing problems where iMovie would crash on launch when plug-ins that add compatibility for video and audio formats that aren't included with QuickTime.
iMovie gets a stability update
iMovie 9.0.8 requires OS X Lion 10.7.4 or higher, and weighs in at 1.08GB. The update is available through Software Update, and as a downloadable installer from the Apple Support website.