#include <QtGui>

class myMainWindow:public QWidget
{
    Q_OBJECT
public:
    myMainWindow()
    {
        tableWidget = new QTableWidget(2,0);
        QPushButton *pb = new QPushButton("Add");
        QVBoxLayout *layout = new QVBoxLayout;
        layout->addWidget(tableWidget);
        layout->addWidget(pb);
        setLayout(layout);
        connect(pb,SIGNAL(clicked()),this,SLOT(addMoreColumn()));
		
    }
public slots:
    void addMoreColumn()
    {

      QTableWidgetItem* itemRow0Column0 = tableWidget->item(0, 0);
      if (NULL == itemRow0Column0)
      {
         tableWidget->insertColumn(0);
         itemRow0Column0 = new QTableWidgetItem(QTableWidgetItem::UserType);
         itemRow0Column0->setText("row 0, column 0");
         tableWidget->setItem(0, 0, itemRow0Column0);
      }
      QTableWidgetItem* itemRow1Column0 = tableWidget->item(1, 0);
      if (NULL == itemRow1Column0)
      {
         itemRow1Column0 = new QTableWidgetItem(QTableWidgetItem::UserType);
         itemRow1Column0->setText("row 1, column 0");
         tableWidget->setItem(1, 0, itemRow1Column0);
      }
      QTableWidgetItem* headerItem0 = new QTableWidgetItem(QTableWidgetItem::UserType);
      headerItem0->setText("Column 0");
      tableWidget->setHorizontalHeaderItem(0, headerItem0);

      QTableWidgetItem* itemRow0Column1 = tableWidget->item(0, 1);
      if (NULL == itemRow0Column1) // it must be null! I never insert an item for that cell!
      {
         tableWidget->insertColumn(1);
         itemRow0Column1 = new QTableWidgetItem(QTableWidgetItem::UserType);
         itemRow0Column1->setText("row 0, column 1");
         tableWidget->setItem(0, 1, itemRow0Column1);
      }
      else
      {
         QString debug = itemRow0Column1->text(); // here debug is "row 1, column 0" !!!!
         qDebug()<<" item at (row 1, column 0) is returned instead of item at (row 0, column 1)";
      }

    }

  public:
    QTableWidget *tableWidget;
};

#include "main.moc"
int main(int argc, char *argv[])
{
    QApplication a(argc, argv);
    myMainWindow mainWindow;
    mainWindow.show();
    return a.exec();
}