New Component

Hi all

i've a problem with creating a new component:
I want to write a ComboBox that filles in all avaible
fonts automatical. her's what I done:

unit FontComboBox;

interface

uses
  Windows, Messages, SysUtils, Classes, Graphics, Controls, Forms, Dialogs,
  StdCtrls;

type
  TFontComboBox = class(TComboBox)
  private
    { Private declarations }
  protected
    { Protected declarations }
  public
    constructor Create(AOwner: TComponent);override;
    { Public declarations }
  published
    procedure UpdateFonts;
    { Published declarations }
  end;

procedure Register;

implementation

procedure Register;
begin
  RegisterComponents('Eigene', [TFontComboBox]);
end;

constructor TFontComboBox.Create(AOwner: TComponent);
begin
Inherited Create(AOwner);
UpdateFonts;
end;

procedure TFontComboBox.UpdateFonts;
var
Index: integer;
begin
Clear; <-- Error here
For Index:=0 to Screen.Fonts.Count-1 do
    Items.Add(Screen.Fonts[Index]);
end;
end.

But everytime I create my new component in desgin-time
(I mean by dragging it on a form) or manipulating the items-property at runtime, I get the error-mesage:" Control '' has no parent window"

What's wrong?

regards
rene