After last weeks windows updates, printing the contents of a radwindow causes a 404 error. Our users little to my knowledge print out the window contents for various reasons. This behavior is also true from your demo @ http://demos.telerik.com/aspnet-ajax/window/examples/overview/defaultcs.aspx right click the window and select print, 404 is what get's printed.
Please advise as we are in a critical state with some of our operations because of this. It does not seem to be an issue with IE10.