The SearchDialog is placed based upon a parent window of type "Window". However, when I use other types like "RadRibbonWindow" as my main window the placement does not work correct. As a result the SearchDialog is shown in the upper right corner of the desktop. This is the code (in SearchDialogController.cs):

        Window GetParentWindow()
        {
            return (this.model.PageScrollViewer == null)
                ? null
                : this.model.PageScrollViewer.FirstParentOfType<Window>();
        }

At least this method should also take RadRibbonWindow in account (this is certainly not used that rarely since we all use Telerik components!) or for a more generic solution look for types that are derived from Window.