Crash after adding a new voice to score

This has happened on several of my files, and it's frustrating.

I've got a complete score, which I've worked on periodically. Now I add a new voice, today a Vocals part. (Other times it has crashed on Cymbals or on Double Bass.)

So far, it's okay. Then I adjust the title of the voice from "Vocals" to "Girl (vocals)" and it quits - several times.

On the last time, it fails completely. Now it has zero bytes, and cannot be opened. Help!