To reproduce:

public Form1()
{
    InitializeComponent();

    RadDiagramShape shape = new RadDiagramShape();
    shape.Text = "Shape1";
    shape.AllowCopy = false;
    shape.AllowPaste = false;
    shape.AllowDelete = false;
    shape.AllowCut = false;
    shape.Position = new Telerik.Windows.Diagrams.Core.Point(50, 50);
    shape.BackColor = Color.Red;
    this.radDiagram1.AddShape(shape);
}

Workaround: Hide the first tab in the SettinsgPane as it is demonstrated in the following article: http://www.telerik.com/help/winforms/diagram-settings-pane.html