Comment 4 for bug 87522

Same problem here with a GeForce 7900 GS.

The problem might be linked to the fact I also have an internal nvidia graphic card (6150) and only occurs with nvidia binary drivers. Use lspci to detect the bus your gcard is connected to then manually change it in xorg.cong works also.

sudo dpkg-reconfigure xserver-xorg

doesn't detect the right port, you have to provide it manually.