Could be a damaged Word data key in the Windows registry. Close
Word 2007, start regedit, and rename the
"\\HKEY_CURRENT_USER\Software\Microsoft\Office\12.0\Word\Data"
key. Word 2007 will create a new Data key using the factory
default settings when you restart the program. If this fixes the
problem, great... but you might have to re-select some of your
Word Options settings. If it doesn't, you can close Word 2007,
go back into regedit, delete the newly created Word data key, and
rename the old key back to its original name to retrieve your old
Word Options settings.