java.lang.IllegalStateException ¿qué significa?

Estoy desarrollando una aplicación de video. Después de terminar la reproducción del primer video, en "OnCopletion" estoy tratando de comenzar uno nuevo. Pero simplemente se detiene (no se bloquea) y no hace nada. En el registro:

10-19 09:44:49.056: ERROR/MediaPlayer(4654): setDataSource called in state 128
10-19 09:44:49.056: WARN/System.err(4654): java.lang.IllegalStateException
10-19 09:44:49.056: WARN/System.err(4654):     at android.media.MediaPlayer.setDataSource(Native Method)
10-19 09:44:49.056: WARN/System.err(4654):     at ru.osiris.BusAdvertising.BusAdvertisingActivity.onCompletion(BusAdvertisingActivity.java:1255)
10-19 09:44:49.056: WARN/System.err(4654):     at android.media.MediaPlayer$EventHandler.handleMessage(MediaPlayer.java:1304)
10-19 09:44:49.056: WARN/System.err(4654):     at android.os.Handler.dispatchMessage(Handler.java:99)
10-19 09:44:49.056: WARN/System.err(4654):     at android.os.Looper.loop(Looper.java:123)
10-19 09:44:49.056: WARN/System.err(4654):     at android.app.ActivityThread.main(ActivityThread.java:4627)
10-19 09:44:49.056: WARN/System.err(4654):     at java.lang.reflect.Method.invokeNative(Native Method)
10-19 09:44:49.056: WARN/System.err(4654):     at java.lang.reflect.Method.invoke(Method.java:521)
10-19 09:44:49.056: WARN/System.err(4654):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:868)
10-19 09:44:49.056: WARN/System.err(4654):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:626)
10-19 09:44:49.056: WARN/System.err(4654):     at dalvik.system.NativeStart.main(Native Method)

¿Qué significa eso? ¿Cómo puedo arreglarlo? ahí está mi código:

public class BusAdvertisingActivity extends Activity implements LocationListener, OnBufferingUpdateListener, OnCompletionListener,
OnPreparedListener, OnVideoSizeChangedListener, SurfaceHolder.Callback {
...
    private MediaPlayer mMediaPlayer;
    private SurfaceView mPreview;
    private SurfaceHolder holder;
    private String path;
    private Bundle extras;

     @Override
    public void onCreate(Bundle icicle) {
        mPreview = (SurfaceView) findViewById(R.id.surface);
        holder = mPreview.getHolder();
        holder.addCallback(this);
        holder.setType(SurfaceHolder.SURFACE_TYPE_PUSH_BUFFERS);
        extras = getIntent().getExtras();
    }
 public void surfaceCreated(SurfaceHolder holder) {
        Log.d(TAG, "surfaceCreated called");
        playVideo();
}
private void playVideo(Integer Media) {
        Log.d(TAG, "playVideo called");
        doCleanUp();
        try {
           File clip=new File(Environment.getExternalStorageDirectory(),
                            playList[FLcurrentVideo].substring(2,            playList[FLcurrentVideo].length()-1)+".mp4");
           path = clip.getAbsolutePath();
           mMediaPlayer = new MediaPlayer();
            mMediaPlayer.setDataSource(path);
            mMediaPlayer.setDisplay(holder);
            mMediaPlayer.prepare();
            mMediaPlayer.setOnBufferingUpdateListener(this);
            mMediaPlayer.setOnCompletionListener(this);
            mMediaPlayer.setOnPreparedListener(this);
            mMediaPlayer.setOnVideoSizeChangedListener(this);
            mMediaPlayer.setAudioStreamType(AudioManager.STREAM_MUSIC);


        } catch (Exception e) {
            Log.e(TAG, "error: " + e.getMessage(), e);
        }
    }


public void onCompletion(MediaPlayer arg0) {

        Log.d(TAG, "onCompletion called");
        FLcurrentVideo++;

        File clip=new File(Environment.getExternalStorageDirectory(),
                playList[FLcurrentVideo].substring(2, playList[FLcurrentVideo].length()-1)+".mp4");
                path = clip.getAbsolutePath();

                    try {
                        Log.d ("111", path);
                        arg0.setDataSource(clip.getAbsolutePath());   //I got exception here
                        arg0.setDisplay(holder);
                        arg0.prepare();
                        arg0.setOnBufferingUpdateListener(this);
                        arg0.setOnCompletionListener(this);
                        arg0.setOnPreparedListener(this);
                        arg0.setOnVideoSizeChangedListener(this);
                        arg0.setAudioStreamType(AudioManager.STREAM_MUSIC);
                    } catch (IllegalArgumentException e) {
                        // TODO Auto-generated catch block
                        e.printStackTrace();
                    } catch (IllegalStateException e) {
                        // TODO Auto-generated catch block
                        e.printStackTrace();
                    } catch (IOException e) {
                        // TODO Auto-generated catch block
                        e.printStackTrace();
                    }



    }

Por favor, ayúdame

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