The easiest workaround is to remove the overlay (e.g., set the Overlay property to false or call the set_overlay(false) client-side method). In most cases an overlay is not needed, as it is used only for showing the popup over heavyweight objects like PDFs, Flash or Java applets: http://www.telerik.com/support/kb/aspnet-ajax/window/details/control-is-shown-behind-a-heavy-weight-object-(pdf-flash-activex-etc)