child QDialog/QMainWindow stays on top of QMainWindow

Hi,

I am using PySide on Windows 7.
I have an application with a QMainWindow and I would like when I click Help in the menu to display a new window.
I am able to do that, either using a non modal QDialog or a QMainWindow using the main QMainWindow as parent but when I click back on the main QMainWindow the created child QDialog/QMainWindow stays on top, also this child QDialog/QMainWindow is not displayed in the taskbar and if I minimise the main QMainWindow this child QDialog/QMainWindow is minimised as well.

I have tried creating the QDialog/QMainWindow without a parent but then when call the show or exec method it just flashes and disappear.

Any idea on how I could get this child QDialog/QMainWindow to not stay on top and behave as a separate window ?

Thanks for your help,

Thibault