Spell Checking in Outlook 97

I have got 2 users who are unable to automate their Spell Checking when sending emails - they get an error message and they are asked to run the Outlook/Office setup again. However, no other user is experiencing the problem and more oddly, they do not have the problem when running the spell check in Word.

I thought Spell Checking was a shared component and thus if it did not work in Outlook, it would not work in Word too.

All my users are on a Winframe 1.7 system and are using Office 97.

Thanks