Faulty RAM or suchlike doesn't seem likely to me. (1) It's a fairly new laptop. (2) Such a fault would surely show up in other applications.

This is only happening with Word.

The main installations I've got since reformatting are now these:

Office
Opera
Firefox (w plugins and addons)
Itunes
Avast
Chrome
TextAloud (w Acapela SAPI5 voices - NOT with Word add in)
FLStudio

Are there any known conflicts with any of these programmes? I just can't think what else it could be.

It boils down to this: if I can't resolve this, I really can't go on using Word, which is hardly fair, because it is not cheap.