Wondering if anyone has experienced this problem?

I can load an .xml file into BIAB and it displays and plays correctly. I can make edits, change styles, add bars, etc. But BIAB will not respond to the "Save" or "Save As" command. Even when I try to exit BIAB and it asks if I want to save the file, it won't save it.

Other files save normally.

I'm using BIAB 2018 (520).