zweites Formular lässt sich nicht anzeigen

[ggfan]

Ich will in meinem Programm ein zweits Formular anzeigen lassen, doch irgenwie kommt mit dem Befehl show nur eine Zugriffsverletzung raus.
Kann mir da jemand helfen?

Delphi-Quellcode:

program myToDo;

uses
  Forms,
  unmain in 'unmain.pas' {frmmain},
  unnew in 'unnew.pas' {frmnew};

{$R *.res}

begin
  Application.Initialize;
  Application.CreateForm(Tfrmmain, frmmain);
  Application.Run;
end.

Delphi-Quellcode:

unit unmain;

interface

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

type
  Tfrmmain = class(TForm)
    lstToDo: TCheckListBox;
    cmdNew: TBitBtn;
    cmdchange: TBitBtn;
    cmdDelete: TBitBtn;
    lstSortItems: TListBox;
    procedure cmdNewClick(Sender: TObject);
  private
    { Private-Deklarationen }
  public
    { Public-Deklarationen }
  end;

var
  frmmain: Tfrmmain;

procedure
  SortTasks();

implementation
uses unnew;

procedure SortTasks();
Begin
  showmessage('hallo');
end;

{$R *.dfm}

procedure Tfrmmain.cmdNewClick(Sender: TObject);
begin
  frmnew.Show;
end;

end.

Delphi-Quellcode:

unit unnew;

interface

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

type
  Tfrmnew = class(TForm)
    GroupBox1: TGroupBox;
    txttitle: TEdit;
    GroupBox2: TGroupBox;
    txtday: TEdit;
    txtmonth: TEdit;
    txtyear: TEdit;
    cmdInputNew: TBitBtn;
    Label1: TLabel;
    Label2: TLabel;
    procedure cmdInputNewClick(Sender: TObject);
  private
    { Private-Deklarationen }
  public
    { Public-Deklarationen }
  end;

var
  frmnew: Tfrmnew;

implementation
uses unmain;
{$R *.dfm}

procedure Tfrmnew.cmdInputNewClick(Sender: TObject);
begin
  unmain.frmmain.lstToDo.AddItem(txtday.Text + '.'+ txtmonth.Text + '.' + txtyear.Text + ': ' + txttitle.Text, unmain.frmmain.lstToDo);
  frmnew.Hide;
end;

end.