Zawieszanie się programu podczas pobierania

procedure tform2.download;
begin
   with TDownloadURL.Create(self) do
   try
   application.ProcessMessages;
     progressbar1.Visible:=true;
     URL:=mod1;
     FileName := mod2;
     OnDownloadProgress := URL_OnDownloadProgress;
     ExecuteTarget(nil) ;
     finally
     free;
   end;

 TDownloadProgressEvent = procedure(Sender: TDownLoadURL; Progress, ProgressMax: Cardinal; StatusCode: TURLDownloadStatus; StatusText: String; var Cancel: Boolean) of object;

procedure Tdownolad.Execute;
begin
   with TDownloadURL.Create(self) do
   try
   application.ProcessMessages;
     progressbar1.Visible:=true;
     URL:=mod1;
     FileName := mod2;
     OnDownloadProgress := URL_OnDownloadProgress;
     ExecuteTarget(nil) ;
     finally
     free;
end;

 Tdownolad = class(TThread)
 private
     procedure URL_OnDownloadProgress
        (Sender: TDownLoadURL;
         Progress, ProgressMax: Cardinal;
         StatusCode: TURLDownloadStatus;
         StatusText: String; var Cancel: Boolean) ;
 protected
   procedure Execute; override;
 end;

unit Unit1;

interface

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

type
  TOnProgressEvent = procedure(Sender: TObject; Progress, ProgressMax: Cardinal) of object;

  TThreadDownloader = class(TThread)
  private
    fDownloader: TDownloadURL;
    fCancel: Boolean;
    fProgress, fProgressMax: Cardinal;
    fOnProgressEvent: TOnProgressEvent;

    procedure DoOnProgress;
    procedure OnProgress(Sender: TDownLoadURL; Progress, ProgressMax: Cardinal;
       StatusCode: TURLDownloadStatus; StatusText: String; var Cancel: Boolean);
  protected
    procedure Execute; override;
  public
    constructor Create(Src, Dest: string; Progress: TOnProgressEvent);
    destructor Destroy; override;
    procedure Start;
    procedure Cancel;
  end;

  TForm1 = class(TForm)
    btnStart: TButton;
    btnStop: TButton;
    ProgressBar1: TProgressBar;
    procedure FormCreate(Sender: TObject);
    procedure btnStartClick(Sender: TObject);
    procedure btnStopClick(Sender: TObject);
  private
    { Private declarations }
    fThreadDownloader: TThreadDownloader;
    procedure OnDownloadProgress(Sender: TObject; Progress, ProgressMax: Cardinal);
  public
    { Public declarations }
  end;

var
  Form1: TForm1;

implementation

{$R *.dfm}

procedure TThreadDownloader.DoOnProgress;
begin
  if Assigned(fOnProgressEvent) then
    fOnProgressEvent(Self, fProgress, fProgressMax);
end;

procedure TThreadDownloader.OnProgress(Sender: TDownLoadURL; Progress, ProgressMax: Cardinal;
       StatusCode: TURLDownloadStatus; StatusText: String; var Cancel: Boolean);
begin
  Cancel:= fCancel;
  fProgress:= Progress;
  fProgressMax:= ProgressMax;
  Synchronize(DoOnProgress);
end;

procedure TThreadDownloader.Execute;
begin
  fDownloader.ExecuteTarget(nil);
end;

procedure TThreadDownloader.Cancel;
begin
  fCancel:= True;
end;

procedure TThreadDownloader.Start;
begin
  Resume;
end;

constructor TThreadDownloader.Create(Src, Dest: string; Progress: TOnProgressEvent);
begin
  inherited Create(True);
  FreeOnTerminate:= True;
  fCancel:= False;
  fOnProgressEvent:= Progress;
  fDownloader:= TDownloadURL.Create(nil);
  fDownloader.URL:= Src;
  fDownloader.Filename:= Dest;
  fDownloader.OnDownloadProgress:= OnProgress;
end;

destructor TThreadDownloader.Destroy;
begin
  fDownloader.Free;
  inherited Destroy;
end;

//====================== TForm ==========================

procedure TForm1.OnDownloadProgress(Sender: TObject; Progress, ProgressMax: Cardinal);
begin
  ProgressBar1.Max:= ProgressMax;
  ProgressBar1.Position:= Progress;
end;

procedure TForm1.FormCreate(Sender: TObject);
begin
  fThreadDownloader:= TThreadDownloader.Create('http://cost_tam',  'D:\jakis_plik', OnDownloadProgress);
end;

procedure TForm1.btnStartClick(Sender: TObject);
begin
  fThreadDownloader.Start;
end;

procedure TForm1.btnStopClick(Sender: TObject);
begin
  fThreadDownloader.Cancel;
end;

end.