sometimes the nitobi assets do not copy over to your site.
make sure you have the following folder in your site:
Nitobi/Assets/script/
and that is contains the following 2 files at least:
nitobi.toolkit.js
nitobi.grid.js
if that folder is not present or those files do not exist in that location, you can manually copy them from:
C:\Program Files\Nitobi\Complete UI 2008 Q2\javascript_css\script