Thanks for the reply. I take your points and sorry for the petulance.

I have run word in safe mode and also disabled all com addons, but the problem seems to be getting worse. Even a hard reboot doesn't stop it. At the moment, I am - sometimes - able to save work in small temporary files. So size may be an issue. But often even those won't save, so am forced to paste into a txt file. I have done an install repair to no avail. At the moment, I'm thinking it will have to be either a complete reinstall or hard disk reformat.