Sometimes - without warning - an FCP/FCE project is unable to be opened, recently I lost a lot of work this way. I took a closer look at this nightmare and found a way to avoid playing this game of Russian Roulette!

One symptom of the bug is that the faulty project file is much bigger than previous versions which are hopefully stored in the Autosave Vault folder.

The problem begins when you drop a video or graphic alias from the browser onto an input well of any video transition, filter or generator. The workaround is to hold down the Control key and click onto the alias in the browser and select the option Duplicate as Master Clip. Then you can drag and drop the new master clip onto the input well of the effect in the viewer window. You should then delete the duplicate in the browser as it is no longer needed, thereby preventing the same Master Clip being used twice.

Summary: Master Clips should be dropped onto the input gadget of an effect in a project once only.