Microphone starting muted on AIR application SDK 2.5

According to the documentation

http://help.adobe.com/en_US/air/reference/html/flash/media/Microphone.html

"Content running in the AIR application sandbox does not need permission to access the microphone and no dialog is displayed. AIR content running outside the application sandbox does require permission and the Privacy dialog is displayed"

But I'm having problems starting the Microphone object, which starts muted and permissions need to be given right clicking on the flash object.

This function returns always true before permissions is given:

public function isMuted():Boolean {

var mic:Microphone = Microphone.getMicrophone();

return mic.muted;

}

The swf loaded is inside the application sandbox, but it's failing also from the debugger.

Any ideas what else to look?

Thanks,

Guille