Why wont these particular projects load and next steps?

I'm working on a 16 minute short film. At some point, something must have changed in my project that is causing a problem where it gets stuck loading it, stays there forever, and I have to force quit.I have duplicated and made a snapshot of the project but the problem persists. I have deleted preferences and render files. Same thing. If I do itI don't think I added any media nor any new plugins when it started acted weird.I have found one annoying workaround which is if I open up an earlier project in the library and then try to open up one of these problematic projects it will sometimes open.Any other suggestions? I'm at a loss of how to fix this. (And it's completely messed up my work schedule!)Thanks......