Did you use the default styles for all of your headings ie Heading 1, Heading
2, Heading 3? If so, try this (but make sure you've saved the document ...
just in case):
Put the cursor somewhere in your TOC (use the cursor keys if hyperlinks
don't allow you to click in it). Insert > Index and Tables; on the Table of
Contents tab, in the Print Preview area; does it show all 3 levels ie Heading
1, Heading 2, Heading 3? If it does, click OK and OK again (when it asks if
you want to replace the selected table of contents). If your TOC isn't any
different then, I'm sorry, but I'm not sure why.
However, if it doesn't show 3 levels in the Print Preview area, click the
Options button and type 3 in the Heading 3 TOC Level box. OK > OK > OK. That
might cure it ... or maybe you created your own styles ... or even just
formatted text to look like a heading, in which case, let me know and I'll
try to help you further?