QGraphicsscene.sceneRect on Windows platform

[sanku3]

In Qt 4.5 version, sceneRect of QGraphicsscene on Window, giving wrong
co-ordinates

I have small program (attaching the file) where I am adding QGraphicsText
item to QGraphicsRectItem , QGraphicsRectItem is added to QGraphicsscene.
when queried for QGraphicsscene.sceneRect its giving wrong co-ordinates as
compare to itemsBoundingRect

QGraphicsScene.sceneRect PyQt4.QtCore.QRectF(-1.0000000000
000001e-05, -1.0000000000000001e-05, 226.00001, 224.00001)

QGraphicsScene.itemsBoundingRect PyQt4.QtCore.QRectF(34.0, 80.0, 192.0,
144.0)

I am working on window xp professional version 2,python-2.6 and qt 4.5

But the same on linux ubuntu 10.4,python 2.6 and qt4.6 is fine, can anyone
suggest where is this difference

thanking you