Error Creating Control: Parser Error DocHeader does not have a property named 'cc3:MyItems'

I am having problems getting this webcontrol working properly. Everything
else works fine except having items. So here is the low-down on the control:

1. The control class is declared as shown below (only relevant code
presented). Notice that it contains a collection of items (not presented
here for the sake of clarity):

[DesignerAttribute(typeof(DocHeaderDesigner), typeof(IDesigner)),
DefaultProperty("Items"),
ToolboxData("<{0}:DocHeader runat=server></{0}:DocHeader>")]
public class DocHeader : System.Web.UI.WebControls.WebControl,
INamingContainer
{
// This member holds all the items associated with this control
private DocHeaderItemCollection items = new DocHeaderItemCollection();

// And this is the accessor property
public DocHeaderItemCollection Items
{
get { return this. items; }
set { this.items = value; }
}

}