My week 13 Imac 27" has always made the buzzing noise coming from the top left of the computer when brightness is reduced below 70%, but I really couldn't hear it much when sitting directly in front of the screen so I lived with it. Now, after having had the computer for almost 40 days, there is an additional noise that I first thought was a fan coming on, but I don't believe it is. It's not the original buzzing, but more like an increased fan noise, though the fans rpms remain at their original normal levels. I see that I can get rid of the noise by moving up the brightness to maximum, and then down to minimum a few times. This works, but then eventually the this new fan-like, or higher pitched noise kicks in again. Any ideas on what this could be. I realized that increasing the brightness for the buzzing was like turning a halogene lamp up so that the regulator stopped making a similar noise. But now this has been added to the problem. Again, it disappears after sliding the brightnes up and down a few times (the original buzzing always remains though at the lower brighntess). Any clues of what I am dealing with?