If the scratch disk used by Final Cut Pro cuts out in the middle of an export, Final Cut Pro becomes unstable: the next time you try to launch it, it will crash on startup.

Fortunately, it's pretty easy to fix. Delete the following preference files:

~/Library/Preferences/com.apple.FinalCutPro.plist ~/Library/Preferences/Final Cut Pro User Data/Final Cut Pro 6 Preferences ~/Library/Preferences/Final Cut Pro User Data/Final Cut Pro Obj Cache ~/Library/Preferences/Final Cut Pro User Data/Final Cut Pro POA Cache

Thanks to Andy Mees for this tip.