QGraphicsView DragMode error

[Radagast]

Qt 4.4.1
quote from the Assistant:

dragMode : DragMode
This property holds the behavior for dragging the mouse over the scene while the left mouse button is pressed.

and here is my code

#include <QtGui>
#include "scenetest.h"
 
sceneTest::sceneTest(QWidget *parent, Qt::WFlags flags)
	: QMainWindow(parent, flags)
{
	ui.setupUi(this);
	Scene = new QGraphicsScene(0,0,500,500,this);
	ui.View->setScene(Scene);
	Scene->addItem(new QGraphicsLineItem(200,200,300,300));
	Scene->addItem(new QGraphicsLineItem(300,300,400,200));
	foreach(QGraphicsItem* item,Scene->items())
		item->setFlags(QGraphicsItem::ItemIsMovable|QGraphicsItem::ItemIsSelectable);
	ui.View->setDragMode(QGraphicsView::RubberBandDrag);
}

#include <QtGui>
#include "scenetest.h"

sceneTest::sceneTest(QWidget *parent, Qt::WFlags flags)
	: QMainWindow(parent, flags)
{
	ui.setupUi(this);
	Scene = new QGraphicsScene(0,0,500,500,this);
	ui.View->setScene(Scene);
	Scene->addItem(new QGraphicsLineItem(200,200,300,300));
	Scene->addItem(new QGraphicsLineItem(300,300,400,200));
	foreach(QGraphicsItem* item,Scene->items())
		item->setFlags(QGraphicsItem::ItemIsMovable|QGraphicsItem::ItemIsSelectable);
	ui.View->setDragMode(QGraphicsView::RubberBandDrag);
}

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So why do I get that RubberBand even if I drag the mouse with Mid or right button pressed?
btw with ScrollHandDrag mode I get the expected behavior - only with left button pressed the view scrolls.