Reinstall Word
The Problem:
Word has gotten so flaky it's barely worth using. Sometimes it starts okay but then hangs; sometimes it gives me errors about there being no space on my hard disk or being unable to save a file; and sometimes it produces registration errors on startup. I've tried using Help 
Detect and Repair, but it hasn't fixed the problem.
The Solution:
What you need to do is back up all critical Word files and then reinstall Word from the Office CD or from the installation cache on your hard disk.
See the bulleted list in the previous Annoyance ("Move Word to Another Computer") for details on the items that you should back up. To reinstall Word, choose Start Control Panel Add or Remove Programs, click the Office item, and click the Change button. In the Office Setup Wizard, follow the procedure for reinstalling Office. In Office 2003, choose the Reinstall or Repair option; in Office XP or Office 2000, choose the Repair Office option. You may need to provide your Office CD.