Qt application quit menu stops painting QGraphicsView content on Mac OS

Dear All,
I am using Qt 4.7.3 and in my application when I select "Quit" option from application menu on Mac OS, application shows moddl dialog (handled closeEvent of QMainWindow) for session save, at this time the QGraphicsView in application windows stop painting its content (QPushButton added as widget in QgraphicsView).

This use case is working fine on windows , no painting issue.

Event if I select close button on top left section of window its working fine, no painting issue but clicking close button and clicking quit menu item has different call stack internally that might be the cause.

Please help, if anyone has any idea.

Thanks,

For the mentioned issue, I added some log entries in the code and from it I found that clicking "Quit" menu item makes QGraphicsView widgets either disable/invisible, can anybody tell me the reason behind it and how to avoid it.

This is on Mac OS only.

Thanks,