Re: GTX 280 screeching...
On my card (8800gt) as with others the squeal is heard if you have a very high frame rate.
Like in some games when intro movie is seen, the fps can be in the thousands.
So just enable Vsync to force 60fps and the noice should be gone. If it is in fact from the card that is and it's same issue as some g80 and up suffers from.
If what above is true for you, then you need not worry about it.