Why am I getting: threadid=3: reacting to signal 3 and game freeze (AndEngine)?-Collection of common programming errors

I’m using AndEngine to make a game that deals with a lot of moving sprites. It’s inconsistant when, but eventually I get a message in the log cat (threadid=3: reacting to signal 3) and the game freezes. What does this error mean? I’ve narrowed down in the code where it happens (it’s marked):

private void levelComplete(){
        runOnUiThread(new Runnable() {
            public void run() {
                 Toast.makeText(TestGFX5Activity.this, "Level Complete", Toast.LENGTH_SHORT).show();
            }
        });
        Log.e("Level Complete","Going to reset values");
        //Reset values
        level++;
        fillerCount = (originalNumberOfFillers + level - 1);
        areaFilled=0;
        fillAreaPercent = 0;

        //Rid scene of sprites
        for(int x=0;x