Is there a new mighty mouse out? I brought mine about 8 months ago but it broke - UPS just delivered a new one to me from Apple and it feels completely different - compared to my old one the button action is ultra unresponsive, I have to really hold down the mouse button hard for it to register as a 'click'. The noise it makes is also 10x louder. It's horrible. Is this a new design or have I got a dud?