Can anyone explain this problem.

I have a fax form for my internal company users which has some protected
sections. For example, the "To" and "From" areas are a form which is
protected. The comments are are a free form area where they can change
fonts, spellchech, and whetever

However, on some machines, the "Spell Check" menu function is disabled, but
it still works using the f7 key!

Can anybody explain whats going on here, its very disconcerting...

Office XP (2002)...