And to add to this a little background...last week this burned fine. I opened it today and it was corrupt.
What changed?
The "creating subtitles" behind the error message suggests looking at anything that changed in the subtitles.
And yes, nothing may have been changed, but something "changed."
Very complicated project, and not one I would want to start over.
I do nto use "Save As" as a way to backup Encore projects (because mine are not that hard to start over, and some many things break Encore projects, I don't trust Save As!), but I hope you did! I'd pick up at a previous one that worked.