I have a rMBP with the 256GB drive, and it's amazing how quickly your drive space disappears when you start working with a little HD video... So I followed the instructions on this page, and created a new iMovie library on an external drive. Then I copied all my events to the new library. But when I delete the original events from my internal drive, my projects stop working, indicating they are missing various clips. Does anyone know how to repoint the projects to the new library location or move the projects themselves to the external drive so they start working again?