[Matt Shea]

I know this thread is old, but I just came across the problem myself. “Greg Strange’s” post above is useful, though if it doesn’t help you you’ll need to take one more step. I was missing the “Bad TV” effect, possibly others.

First, quit Final Cut Pro and follow Greg’s instructions above to insure you have the necessary files in your library.

Then follow the instructions here (From Apple’s support site) to delete your FCP user preferences. This shouldn’t affect any projects you have, but will of course reset your preferences and saved settings to default:
1. In the Finder, go to ~/Library/Preferences—the tilde (~) represents your Home folder.
2. Remove the “com.apple.finalcutpro.plist” file from the Preferences folder.
3. Remove the “Final Cut Pro User Data” folder from the Preferences folder.

Launch Final Cut Pro. It may take a minute or two longer the first time to rebuild those files. Your effects should now be back.