Thanks for that ORAC, I've looked at the site - very useful, but as it happens I think I have 'cracked it', if it is of use to anyone else.
In my Windows directory there was a file '***.xlb', *** being my profile name. There was NO file like that for my wife's profile. I deleted this file and it 'reformed' under the same name, and all is now ok. The programme was obviously loading that file in my profile but not in hers and it was presumably corrupted.