Josh, I found this solution elsewhere thart worked for the iMovie problem:
Hi
Called Apple support and they had me remove the Prefs files without going through Terminal as follows:
In finder
Click Go from menu bar
Click Go to Folder
Enter ~/Library
Click Go
In Preferences select com.apple.iMovieApp.plist, and com.apple.iMovieApp.plist.lockfile
Drag to desktop
Restart
Launch iMovie - all should be well :-)
However, in my case that was not what happened so I repeated the process above again but before launching iMovie I moved all of my iMovie Projects and iMovie Events from the Movies folder to the desktop.
On launching iMovie this time all worked well - obviously there were no events of projects in there.
Am going through the process of importing each in turn - I guess one must have been corrupt or the filepath incorrect - who knows.
Suffice to say I have iMovie up and running once again :-))
Hope this works for you too :-))
John