I have the same problem. Document has origins dating to 1996 and is currently 342 pages long with more than 900 footnotes. I have recently switched from Word 2003 to Word 2010 and cannot save in new format. In response to error message, have deleted all graphic objects yet when searching for graphics objects search reports that 2 exist. Curiously, when searching, both objects appear to be located a single footnote. They are definitely not evident! Have deleted footnote to no avail. As far as I can tell I do not have any text boxes, callouts (?), or endnotes.