That's a symptom of a Word Data Key corruption - usually because Word has
been running when updates are installed.
Run Regedit and expand by double-clicking to the key below. With DATA
selected, press DELETE. Word will automatically recreate a new key when it
is restarted.
HKEY_CURRENT_USER\Software\Microsoft\Office\12.0\Word\Data
Symptoms of Data Key corruption include:
• The mouse does not work when you use Word.
• You cannot open a Word document from the Search window in Windows
Vista.
• You cannot open a Word document from Windows Desktop Search.
• Word crashes when you try to start or exit Word.
• Word crashes when you open the Open dialog box.
• Word crashes when you save a document.
• Word crashes when you close a document.
If you feel uncomfortable editing the registry yourself, Microsoft have a
fix that will do this for you.
http://support.microsoft.com/kb/940791 and press FixIt
