Re: MS Word and complex documents
This is also a problem I've had in the past when I've been running Adobe Acrobat in the same session. The two programmes don't seem to like each other! If you've even been viewing a .pdf (with Acrobat) file during your 'computing session', you may need to reboot before you reopen the Word document.
However, I think that the fast save option being turned off may well be the answer - dastardly thing that feature!