Windows 7: Clicking sub-menu before its automatic appearance is preventing from displaying it

When using a menu having sub menus, it should be possible to immediately popup a sub-menu by clicking on the corresponding item or by moving the cursor on this item and waiting a little (400 ms).

Just after opening the main menu, moving the mouse to the desired sub-menu and clicking on it before the 400 ms is not opening the sub-menu and waiting or clicking again is not working.

The other items in the menu are working fine...

I have notice a small flickering of the menu at the end of the animation and under debugger the action is not found in the first QMenu::mouseMoveEvent(). Disabling the animation using the following code is a workaround:

QApplication::setEffectEnabled(Qt::UI_AnimateMenu, false);