In IE 8, user relationship form pop up coming when clicking the chat or user to initiate chat

hi,

I am have problem with working with DrupalChat in IE 8.
When i click on chat it pops up the user relationship form popup and load the whole page in there.
In user_relationships_ui.js there is a form popup functionality that lets you choose the options on the same page.
when click on the chat, this form is poping up only on some pages for IE, for firefox everything is fine.

IE gives javascript error :
drupalchat.js line 100, Object doesn't support this property or method.

Is anybody else getting the problem.

thanks