When upgrading some installations of Microsoft Office to Office 2007 certain problems can arise.
We had problems with Word shutting down after the upgrade.
It wouldn't!

To repair checkout this Microsoft article. http://support.microsoft.com/default.aspx?scid=kb%3Ben-us%3B921541
Download the "Guided Help" and run the EXE. This automatically repaired our installation and Word works perfect!!!!