I believe the error message would be "No table of contents entries found."
This would be a result of having a TOC field in a document with no headings
or paragraphs formatted with an outline level other than Body Text. If you
just want to get rid of the TOC field, select and delete it (if you want to
see the field code, press Alt+F9). If you want to have a TOC that works
properly, then you'll need to tell Word what goes in the TOC; see http://www.ShaunaKelly.com/word/toc/CreateATOC.html