there are hacks, but none are pleasant.
I've been looking into this. At first I thought that the absolute latest nVidia driver (195) and settings util has an overscan compensation option, but while it works for VGA, HDMI people don't seem to get this option:(
The primary hack I can find on this stems from the EDID data that the TV sends the nVidia driver. It appears that the driver misinterprets this data (or the data is flawed somehow). Successful hacks I've found either
1. over-ride the EDID settings on the driver completely, and manually set up X for the display
2. capture the EDID data, edit it to be correct, and instruct X to use this new EDID instead. (See here for an example
Neither of these are easy to do however, especially since there are so many different types of Bravia set with different capabilities. I can confirm that Neuros are trying to establish some kind of fix for this problem, but it might take time.