I just bought and received a new 21.5'' iMac and love it but the screen is making a high pitched noise, similar to a dog whistle. It's that sound that isn't loud but pierces through your brain. And the brighter the backlight is, the louder is gets. What do you guys think? I love this machine but I don't think it should be doing this and it bothers the heck out of me. I called Apple and all they said was to bring it to the Genius Bar.