QDialog: On Vista QDialogs application bar breaks if changing to Windows Classic style while running.

On Vista QDialogs application bar breaks if changing to Windows Classic style while running. The application bar is too small(height) and the close button is very small.

#include <QtGui/QApplication>
#include <QDialog>
#include <QtGui>
class myMainWindow:public QMainWindow
{
public:
myMainWindow(QWidget *parent=0):QMainWindow(parent)
{
QWidget *dlg = new QWidget;
setCentralWidget(dlg);
setWindowTitle (QString ("Test Application"));
QDialog* qdlg = new QDialog (this, Qt::Tool);
qdlg->setWindowTitle (QString ("Testing QDialog with Qt::Tool flag"));
qdlg->show();
}
};
int main(int argc,char* argv[])
{
QApplication app(argc,argv);
myMainWindow *cb = new myMainWindow();
cb->show();
return app.exec();
}