Now I undestand the error you get.
No, the landmarks usually go into the XHTML TOC which replaced the "old" NCX TOC.
Please read the specifications (I gave you the relevant link in the post above) and/or inspect some examples of EPUB 3 files, e.g. from:
http://code.google.com/p/epub-samples/
or
http://www.smuuks.it/index.php/en/projects