Well I did some changes in the .capx file you have created, mainly removing the .mp3 (capture/encode/play) functions, put the "Init Microphone" action in the "Start of Layout" event and do not hide the 'Flash Microphone Panel" and now is working well in all four browsers, IE9, FF, Chrome and Opera. I changed too the "Save" action but it needs more develop, the main issue is than you can not clean the "AudioBase64" object string, setting "" to it, because do not work. So I am destroying and creating new "AudioBase64" objects for each "Play" action.
My altered .capx
But I found a post in with the author explained another method of obtain HTML5 "camera-and-microphone-access", so I wanna ask if you think it is better than the one you did? If it is, do you know how to put it in yours or a new plugin?
HTML5 Camera and Microphone Acess