We can probably help, but first you'll have to explain how you're managing
to run Office 2008 on Jaguar... Office 2008 requires OS X 10.3.9 (Tiger) or
later.
Exact version & update levels of both Office & OS X need to be specified as
well as a fuller description of the problem. How are you going about it,
exactly what happens as a result & how does that result differ from your
expectations? Editing in a Header or Footer isn't really any different than
working in the body content, so we need the details in order to determine
what might be going awry.