This just started happening to me today too. I need to click where the buttons usually are, but the screen is inverted. The letters are still correctly written from left to right, except that they are upside down. Yesterday I played the voltz pack just fine.
For some reason, when I first started up the voltz pack today, it seemed to re-download something, although I already had the newest update. The entire game is upside down, not just the startup screen. I don't think I can get used to it, although it is a little fun at first :)