Hi Yelly:
Karl Petersen (iMovie Guru)quote:
Do you have any third-party QuickTime add-ons installed? Users have reported lots of weird problems associated with any of these: 3ivx, Divx, Flip4Mac. If so, remove them—or temporarily move them to some other folder—and Restart your Mac.
They may be located in the Hard Disk>Library>QuickTime folder, or your User>Library>QuickTime folder.
If that doesn't help, remove any third-party iMovie plug-ins too. They are located in your User/Library/iMovie folder.
Sue