I've updated to version 10.1 and now FCPX won't open!

Go to ~/Library/Application Support/Final Cut Pro and move the "Layouts" folder to the trash.

(hold down the option key and click the Finder "Go" menu to gain access to the Library folder; then navigate to thee indicated subfolders)

I had the same problem and removing the Layouts folder worked. Now FCPX10.1.1 opens and I see the libraries in the libaries pane but they won't open. Only one or two will opens. All external drives are connected. ??