If I have a document, whatever length, and decide that perhaps I want a word
in bold or whatever, I will highlight it and set it bold.

What happens however is the WHOLE document then goes bold and by using Ctrl
Z twice I can get the document back where it should be and the bit I wanted
changed, changed!  I use the example of setting Bold, but it can be
justification, types size, face - whatever.

I have demonstrated this to a colleague and then emailed it to him where the
phenomona does not appear.
Most odd and very annoying!

Any ideas!  Using Word 2000