PictureCallback.onPictureTaken never called

I am writing an application that needs pictures taken with the camera. The problem occurs when I try to take an actual picture. Here's the code that is troubling me:

    final ShutterCallback shutterCallback = new ShutterCallback() {
        @Override
        public void onShutter() {
            Log.d(TAG, "onShutter");
        }
    };

    final PictureCallback callback = new PictureCallback() {

        @Override
        public void onPictureTaken(byte[] data, Camera camera) {
            Log.d(TAG, "onPictureTaken - jpeg");
            try {
                //async task for storing the photo
                new SavePhotoTask(CameraView.this.ctx, data).execute();
            } catch (final SavePhotoException e) {
                //some exceptionhandling
            }
        }
    };
    this.camera = Camera.open();
    this.camera.setPreviewDisplay(surfaceHolder);
    final Camera.Parameters parameters = findBestParameters(w, h);
    this.camera.setParameters(parameters);
    this.camera.startPreview();
    Log.d(TAG, "takePicture now!");
    this.camera.takePicture(shutterCallback, null, callback);

On the emulator it seems to work out but on my phone (Motorola Defy - android 2.1).

The actual problem: on the phone the picturecallback is never happening "onPictureTaken" gets never called. The Shuttercallback is executed but the other is not (and I tried with raw instead of jpeg, same thing).

Does anyone know this problem? I just don't see where the difference lies to the emulator right now. I appreciate your help.