Issues in Reorder list - C#

I am using Reorder list in my page. In IE it is working properly. 开发者_JS百科But in Firefox it is not working properly. I am not able to reorder the last few items. Can any one of you tell what may be the problem?

take a look http://www.asp.net/AJAX/AjaxControlToolkit/Samples/ReorderList/ReorderList.aspx