Application crash on modal dialogs when switching QPlugins

I have an application that works with several QPlugins (actually .dll). Only one can be loaded at a time.

The application crashes every time it needs to display a modal dialog after reloading a QPlugin.

1. load QPlugin1
2. load QPlugin2
3. call to a modal dialog (ex : QMessagebox::warning)
4. crash at strong*qapplication.cpp : l. 4562*strong

Joined a small application that :
loads a plugin1, unloads it, loads plugin2 and call a modal dialog on this one.

I created a thread on the forum here :
http://qt-project.org/forums/viewthread/26104/
I am not the only one that encountered this issue :
http://qt-project.org/forums/viewthread/7344/