I hear the Buzz on my 450. But it sounds like it is coming from only the side where the power is . Check the location, does it sound louder on one side versus the other?
I still say it is a power issue or an improper ground in there. I also remember my 32" CRT making a buzz noise all the time, its just a TV noise.
My noise is tolerable and sounds like a normal TV, yours may differ.
Also, it almost sounds like florescent lighting but a little bit more high...