We recommend you use the oWnd.show() function every time when you need to show the RadWindow
control from client side code. This function performs some additional initializations in the RadWindow
itself that are needed in order to work properly. If instead of show() some other function like moveTo() or center() is used, there will be problems like the one that you currently have.
An exception is when you use radopen()
function. In this case the show() function is called internally and you do not need to call it explicitly for the newly opened RadWindow
the Telerik team