I have tested both with one of my page (with script written in the page) and with one of your pages (with script written in th firebug console).
i've done the same test on one of your web pages :
then i launch thoses scripts in my firebug console :
var myVarName = $('#tabstrip').kendoTabStrip();
// return undefined
myVarName; // return [div#tabstrip.t-widget]
// throw "toto.tabGroup is undefined"
On both tests i get the same problem.
Can you help me ?