Spontaneous show of minimized window in Qt4 KDE

Question

I'm working on a Qt4 application that shows some strange behavior when minimizing in KDE.

As soon as I minimize the main window, it reopens immediately afterwards. This happens only in KDE. Other window managers like gnome, xfce or icewm work fine. Also, under OpenSuSE, the problem arises only sometimes, whereas under SLES11SP2, the problem arises always!

I checked the events being passed using an eventFilter() method. The QEvent responsible is spontaneous and seems to come from X11. Going further, it turned out that it's an XEvent of type 19 (MapNotify).

My application consists of two QMainWindow, both having several QDialog instances.

Further information:

• Qt 4.7.4
• QMainWindow #1 flags: 0x0800f001
• QMainWindow #2 flags: 0x08013003
• QDialog flags: 0x08013003

I had the impression that it might have something to do with the window flags, but one day of trial and error doesn't show any results so far.

Any kind of advice appreciated.