I had my 2 GHz C2D swapped at work 2 weeks ago for a 2.16 GHz until with a larger hard drive. I NEVER had this issue with the 2 GHz C2D I used for almost a year - every single day.
Today, my new 2.16 GHz MB started making this hissing sound. It's coming from where the power cable connects. Another odd thing is - it starts about 15 seconds of sitting idle with no input from me. As soon as I tap a key on the keyboard, the sound stops. It's not the speakers, CPU/fan, nor the hard drive. I seriously think it has to do with the power coming in.
I am stuck home sick from work, with my work laptop and will not be able to do anything until Monday with it. The sound is driving me up a wall when I am reading e-mails or news stories and what not.
Very Very disappointing. Especially when I was about to buy one of these for myself - the first Macbook was flawless - this one leaves me disappointed and really bitter about it.
The noise is very high pitched, yet low - but enough to drive you mad. I'd expect something like this from an Acer or another cheap discount laptop maker, but not on a 2 week old $1600+ laptop.