Qt 5.2.1 Windows Application cannot be closed by InnoSetup

Hi,

I've been using Qt 5.1.1 msvs2010 opengl along with InnoSetup 5.5.4 and recently I've upgraded to 5.2.1
(skipped 5.2.0 because of QTBUG-35806)

Before upgrading to 5.2.1, InnoSetup was able to close my application (if it's running) and continue installation. After the upgrade, InnoSetup closes my application window but the process persists in memory, which in turn prevents InnoSetup from finishing the installation. After that my application process persists in Task Manager and continues to cause problem unless killed from Task Manager.

The same project built using 5.1.1 doesn't have this problem so I'm guessing it has to do with latest implementation in 5.2.1.

not sure if this is relevant but the environment is:
Apple Macbook Pro with Retina display, Windows 7 running in VirtualBox

Thank you.