Vap/maxell - looked at all of those. Quite bizarre really. All the paths etc appear to be in place, but the message keeps appearing.
I have 'recreated' the custom.dic and no success.
I have decided to uninstall yet again, and this time I will remove all registry references to office and reinstall and see if I can beat this into submssion!
Edit: Uninstall, Spring clean, install and the same
Edit 2: Does the 'Custom Dictionary' language setting matter? Mine shows 'none'.