I am using validatious-custom-0.9.1.js in my project and I am trying to validate required fields for radio buttons. But it is not validating the radio buttons in IE8. I am getting the following error in console

Message: 'tagName' is null or not an object
Line: 7
Char: 9921
Code: 0
URI: http://validatious.org/design/js/val....js?1256063644

The above mentioned line of code is
var B=this.__elements[0].parentNode;
return v2.$(B.parentNode).previous()
var A=v2.$(this.__elements[0]).previous();
return A||this.base()

It works fine in firefox.

Can somebody please help me in this. If this is solved, then this framework will be very useful to avoid all the hardships in validating.