[Jordan Baylor]

I experience this error when I open a Final Cut Project that was created using a version of Final Cut that supported one of the following items differently:

1) “Color Solid”

2) “Chroma Keyer”

3) motion effects of timeline within a timeline that has separate motion effects within a timeline with it’s own motion effects.

My advice would be to just finish up the editing on the computer where the project file was created, and avoid using projects that were created on another computer with your current version of Final Cut.
If that isn’t an option, (i.e. that computer crashed eternally) you may have to continuously experience crashes until you can rework the project file saving frequently, replacing and recreating the above problems until the project is completed. You will still experience crashes when reopening the project, but once you get past the initial crashes of opening the project, you will find it stays open until you come into contact with one of the above problems.