Had to exchange my 5900 Ultra for a 5900 non-Ultra in order to play any games (bad flickering), heck even use 2D (mouse wheel noise and some slight flickering).
"Another interesting piece of information: the card does NOT make the noise unless I have the NVIDIA drivers installed. Both of the latest drivers make the noise."
If you run 3D with the default DX8 driver shipped with windows you don't get the problem?
This means that there might indeed be a fix for at least the noise problem in a future driver.
The flickering problem (which is a much more serious problem for me personally) still seems pretty mysterious though.