Empty (null-size) Projects

They are as you say, so I began looking at the differences between the two projects that iMovie shows normally, and all the rest that show only as greyed-out empty symbols that don't do anything when selected.

The two projects that do "work" show a file called CurrentVersion.imovieevent and four folders called Original Media (with clips), Render Files, Shared Items, and a folder named after the project that contains Backup.imovieevent, CurrentVersion.imovieevent, and in one case, also Damaged.imovieevent.

The rest of the projects that register as null also show the same CurrentVersion.imovieevent file, plus no folders or one, two or three folders. An Original Media (with clips) folder is almost universally present. Also common but not absolutely so is a folder called Render Files, and/or one called Unsupported Media which usually either just one file called iMovie Data but occasionally includes an actual clip or two (in this case .dv clips). In no case is a project-named folder present in these defective projects, which is a hint to me that the lack of the file(s) they'd normally contain means I'm probably SOL.

So far, no change after deleting certain package files, as on the other thread. Final Cut is overkill, but I still wonder if it is less prone to costly hiccups than iMovie is.

I think I'll research two tacks, the first being how to get iMovie to prompt me to let it fix the library, and second how to best utilize iMovie 8.0.6, which I just now found was never auto-removed during updates. It is apparently still able to see all of the original Events and Projects folders, but is showing me that some raw Events footage is missing, which I may or may not still have the DV tapes for to re-import into it. But many Projects are fully playable and I should at least be able to export them as finished works for safekeeping. This broken Library file problem is now a can of worms, but also potentially offers a method of salvaging at least some projects by horsing with iMovie 8.

Thank you, Rich. Option & Command delete preferences opened what looks to be a clean install with startup windows, no projects and no events. That was disconcerting, at first! Switching over to my own Library showed no change to the problem described.

For some reason, the iMovie backups folder shows only two library backups, the earliest being two weeks ago, which is far too new. Though the Projects are shown in a different order, the blank, empty Projects problem is there as well. Makes me wonder if the latest updates to High Sierra and/or iMovie wiped off earlier such backups. Getting there along the path described was not possible since there is no visible Library folder off my username. I had to search "Library", and look at each path shown below to find the right one. Got there, though.

At first blush it appears that a lot of files/folders referred to aren't used in the new version, but I am copying my library file now and will try some voodoo surgery on the original, just to try something. (It's over 300GB in size.) I went back in Time Machine to try to find older iMovie library backups than I currently have, but the ...Library/Caches/ directory apparently doesn't exist in former versions, and I couldn't spot older backup library files anywhere near there. I'll try the thread you suggest and keep goofing with things. Thanks for your responses!