有关 SHELL 组件的使用问题(50分)

烦请各位帮小弟看下这段代码,不知道是什么问题,在访问网络共享资源时总是
出现:"......EACCESSVIOLATION........!".奇怪的是,在访问本地资源时
却没有任何问题!?
procedure TForm1.RadioGroup1Click(Sender: TObject);
begin
filelistbox1.Clear;
//shelltreeview1.FreeInstance;
//shelltreeview1.Enabled:=false;
if radiogroup1.ItemIndex>0 then
shellTreeview1.Root:='rfNetWork'
else
shellTreeview1.Root:='rfMyComputer';
//shelltreeview1.Enabled:=true;
end;

procedure TForm1.FormClose(Sender: TObject; var Action: TCloseAction);
begin
action:=cafree;
shelltreeview1.Freeonrelease;
application.terminate;
end;

procedure TForm1.ShellTreeView1DblClick(Sender: TObject);
begin
FileListBox1.ApplyFilePath(shelltreeview1.path+'/*.*');
end;

procedure TForm1.FormActivate(Sender: TObject);
begin
filelistbox1.Clear;
shelltreeview1.Root:='rfmycomputer';
end;

gz