If any of Final Cut users are experiencing problems launching FCP 5.1, you should check out this article at Macfixit. Final Cut Pro's user preferences are notorious for causing crashes and like the article suggests, the first thing to do when the app gets wacky is to get rid of user preferences file. And in case you need to save your user preferences, you can use a tool like FCP rescue to save your FCP preferences and other settings. First time I have heard about this app, something I have needed for a while.