Hi, you may reproduce it , for example, on live demo site. http://demos.telerik.com/aspnet-ajax/menu/examples/functionality/scrolling/defaultcs.aspx
. It occurs only in IE 6.0.
Steps to reproduce:
Push mouse button on scroll bar of menu and hold on it. While menu is scrolling, move a mouse over the scroll bar (don't release the mouse button). And menu Items with scroll bar will go up or vanish.
If you want , I can send you screenshots from your demos site with this problem.