The answers for Word 2007 & 2010 are essentially the same, so it's of little consequence that most of the hits apply to Word 2010.
Have you tried repairing the Office installation (via Word Options|Resources|Diagnose)?
You can also get this problem if you're trying to access files on removable media or if there are too many tmp files in your temp folder.
See also:
https://support.microsoft.com/en-us/kb/921541