iPhone - Multitasking / Event.ACTIVATE Event.DEACTIVATE

Hi,

I'm using a native extension to deal with the iPhone's mute button (http://extensionsforair.com/extensions/mute-button/)  but it seems to loose it's way when the application goes into background mode. So what I'm trying to do is figure out when my application regains focus so I can reset it.

I try to do this using:

NativeApplication.nativeApplication.addEventListener(Event.ACTIVATE,BecomeActive)

NativeApplication.nativeApplication.addEventListener(Event.DEACTIVATE,BecomeDeActive)

But whatever I do on my phone - BecomeActive not BecomeDeActive are never called. Do I understand this concept correctly or am I doing something wrong?

Thanks in advance

Leon