Apple has released an update to iMovie, fixing a minor bug and bringing the app to version 9.0.8. The update weighs in at 1.08GB and is available via Apple's support website.
About iMovie 9.0.8
Addresses an issue related to third-party QuickTime components that could prevent iMovie from opening
Update 1:29 PM: The Mac App Store version of iMovie has now been updated to 9.0.8.