Native Installer does not update the existing application

We packaged a native installer on windows and implemented a custom update mechanism (using http://code.google.com/p/nativeapplicationupdater/).

The problem is, when a new updated application installer runs, it does not seem to update an existing installed application.

It just runs the existing app without actually replacing it with the new copy.

If I first manually uninstall the exisintg app and launch the new installer, I do see that the installed application

is newer than the previous one (confirming that the new installer does include a new application version).

Any help is appreciated.

Thanks,

Eilon