iMovie bug? I can't create new project without destroying updated but unsaveable project.

Hi:

I'm running iMovie 10.0.9 on a mid-2009 white MacBook with OS X 10.10.5 (Yosemite)

About 3 months ago, I created a project in iMovie and exported it to Theater and my YouTube account. Everything went fine, no complains.

Since then, I have been updating the project every now and then, and yesterday, feeling pretty satisfied with my creation, I exported to my YouTube account and to File. The File export went fine.

The problems I'm running into now is that the YouTube export didn't work, the Project's thumbnail in the Preview window still shows a still from a shot from the old exported file which I deleted since, and if I create a new project anywhere, the entire project disappears, except -bizarrely- the name and thumbnail.

I'm now stuck in limbo, with a project I can't save, and an iMovie that can't create a new project.

Any help/workaround is greatly appreciated.

Note: I'm very comfortable with the CLI, if that can help me.

Alex