Have you tried repairing the Office installation (via Programs & Features > Microsoft Office > Change in the Windows Control Panel)? Do you have any other Office versions installed?

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Cheers,
Paul Edstein
[Fmr MS MVP - Word]

Thanks for the suggestion - no, I had not, in fact I had quite forgotten about that option. Will try and report back.
This (Home and Student 2010) is the only version installed.

Thanks again, Andrew

Dear Paul

Thank you, it seems to have worked (much to my surprise, the last time I tried that -years ago - it was an abject failure). Really useful suggestion, thanks again, Andrew

PS Thanks for your e-mail about exclusion dictionaries: if you had read what I wrote, you would have seen that I had tried the link without success.