Double-taping on the corner of the window multiple times displays a gray border. At this point, minimizing the main window results in a blurred rectangle remaining where the RadWindow used to be.

To resolve this remove the MinWidth setting. You can set it back when the window is restored.

private double myMinWidth;
private void Window_WindowStateChanged(object sender, System.EventArgs e)
{
            var window = (RadWindow)sender;
            if (window.WindowState == WindowState.Minimized)
            {
                this.myMinWidth = window.MinWidth;
                window.MinWidth = 0;
            }
            else
            {
                window.MinWidth = this.myMinWidth;
            }
}

This can be observed only when AllowTransparance is set to false.

When the Window is opening or resizing and Winforms controls are placed inside its content the content flickers.

It can be reproduced with the Show method of the window or with Dock, ToolWindows and the save - load functionality.

Popup shows behind RadWindow when using two monitors in Windows XP.

As a workaround you can set:  window.CaptionHeight= 0;

Maximizing RadWindow from the header button shows a window with the size of the content if SizeToContent = true. If you maximize with double click on header it is ok.