Back Button

I have 2 questions and I would really appreciate it if you guys could help me out.

1. I've installed the JuceDemo application on my Android device. For some reason the back button doesn't do anything. Why is that ? 

2. I am developing an Android app using Juce audio modules.  The audio works fine. The problem is when I close the app with the back button and re-open it, I get an error in the file juce_audio_OpenSL.cpp, in the constructor of "struct Player"

Problematic code:

check ((*playerObject)->Realize (playerObject, SL_BOOLEAN_FALSE));
check ((*playerObject)->GetInterface (playerObject, *engine.SL_IID_PLAY, &playerPlay));
check ((*playerObject)->GetInterface (playerObject, *engine.SL_IID_ANDROIDSIMPLEBUFFERQUEUE, &playerBufferQueue));

Stack trace:

AudioFlinger could not create track, status -12

AudioTrack::Initcheck status 4294967284

Leaving object::Realize(SL_RESULT_CONTENT_UNSUPPORTED)

Fatal Signal 11

After that the app crashes. 
If I close the app totally from the task manager and then open the app, there is no error. It seems that the calls to Destroy don't free all the allocated memory. Any ideas ? 

Thanks, 
Tal.

There's a nearby thread which may answer your first question : http://www.juce.com/forum/topic/device-buttons