With a weird or intermittent system problem, you can try trashing the Final Cut Pro prefs:
Quit Final Cut
In ~/Library/Preferences (the ~ is your username), delete com.apple.FinalCutPro.plist
In ~Library/Preferences/Final Cut Pro User Data/, delete:
Final Cut Pro 5 Prefs
Final Cut Pro Obj Cache
Final Cut Pro Prof Cache
To reinstall Final Cut Pro:
Open the Applications folder.
Drag the Final Cut Pro application to the Trash.
Go to /Library/Receipts.
In the Receipts folder, select the