That has happened to me a few times, apparently the file becomes damaged and is trashed.  It seems to be related to "use binary morph target" option in preferences, I've disabled it on both installs and it seems to have cleared it up.

I don't think there is a good fix for trying to recover the damaged file (poor error handling on e-frontier's part).

ps: I've gotten in the habit of periodically saving with a new filename when I hit a reasonable landmark in building a scene file just in case this happens to me again.

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