a very basic and simple question which is puzzling me

i want to change the title of the main window in my qt application (the GUI has been designed by Qt Design so I have the ui. and setupui() stuff)

Qt Code:
  1. MainWindow::MainWindow(QWidget *parent) :
  2. QMainWindow(parent)
  3. {
  4. QString windowTitle("some good stuf here");
  5. QMessageBox::information(this, progName, windowTitle );
  6.  
  7. //....
  8. this->setWindowTitle(windowTitle); // ???
  9.  
  10. ledGreen.load(":/bitmap/LED-Green-20.bmp");
  11. ledRed.load(":/bitmap/LED-Red-20.bmp");
  12. ledDark.load(":/bitmap/LED-Dark-20.bmp");
  13. ui.setupUi(this);
  14.  
  15. //....
  16. }
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can't understand what is wrong here ...

thanks much