The 96.XX drivers do not work under the current ubuntu 12.04 version (after 10.10, using the 96.XX drivers got harder, and you had to wait longer for the drivers to work with the newer xorg versions).
Your problem might be- Driver "nv". nVidia doesnt make the "nv" drivers anymore, and I dont think that the nv driver is in 12.04 at all. Try- Driver "nouveau".
BTW, with nouveau in most cases you dont have to use a xorg.conf file to set resolution, etc..