I recently purchased a 21.5" iMac right before Lion was released. I was rearranging things in my room today and had to move my iMac. When I plugged it in it made what I can only describe as a buzzing noise. Even when I shut it down the noise was not as loud but it still continued. The noise didn't completely stop until I unplugged it from the outlet. Is this just a problem with the outlet? Or should I be worried that there's something wrong with my iMac?