Try trashing the tasmanbrowser.cache and the
com.microsoft.browserfont.cache, found in your ~/Library/Caches.
Do you have theCalibrifont installed on your machine?
I just got off the phone with Microsoft on this same issue.
It's a known bug within the Office 2004 team. Some point sizes on
Calibri (Microsoft's own font) do not render correctly in Office 2004
at all. They render fine in Apple applications (i.e. Textedit). It
is a known bug.
Unfortunately, the Office/Windows team have chosen to make Calibri the
default font for messages composed on Outlook 2007.
No word on whether or not the next update fixes this.
--Verm