Please refer to the following
http://forums.asp.net/t/1764862.aspx/1?ModalPopupExtender+throws+JS+error+this+_onHiding+get_animation+is+null+or+not+an+object+
Comments: Please upgrade to the latest version of AJAX Control Toolkit v15.1. If the problem remains, feel free to post a new issue.
http://forums.asp.net/t/1764862.aspx/1?ModalPopupExtender+throws+JS+error+this+_onHiding+get_animation+is+null+or+not+an+object+
Comments: Please upgrade to the latest version of AJAX Control Toolkit v15.1. If the problem remains, feel free to post a new issue.