Word closes when replying to emails in Outlook

XP (sp2) & Office 2003 (sp2)

I have a user that keeps Outlook and Word open at all times during the day,
but occationally when they reply to an email when they hit the send button
word will close.

Word is set as the email editor, and during a quick test it would seem that
not using it as the editor will fix the problem, but we would like to
continue to use word as the editor if possible.

Thanks in advance,

jking