You install an automatic update for Microsoft Office Word 2007 on a Windows Vista (or Windows 7) -based computer and then restart the computer. If Word 2007 was running when the computer was restarted, you experience one or more of the following symptoms:
- 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.
To resolve this problem, delete the HKEY_CURRENT_USER\Software\Microsoft\Office\12.0\Word\Data registry subkey. Close regedit and start Word.
More detail here http://support.microsoft.com/kb/940791