Ok lets try this, open a terminal and then type:
This is to find out which service is your display manager(DM) and the process ID so you can stop it
ps aux | grep -i dm
example here my output:
uki@ubox:~$ ps aux | grep -i dm
root 989 0.0 0.2 19480 3152 ? Ssl Nov22 0:00 gdm-binary
root 1060 0.0 0.3 21552 3640 ? Sl Nov22 0:00 /usr/lib/gdm/gdm-simple-slave --display-id /org/gnome/DisplayManager/Display1
root 1063 0.7 3.7 48792 42260 tty7 Ss+ Nov22 19:55 /usr/bin/X :0 -br -verbose -auth /var/run/gdm/auth-for-gdm-4nREc8/database -nolisten tcp vt7
root 1075 0.0 0.2 19868 3044 ? Sl Nov22 0:00 /usr/lib/gdm/gdm-session-worker
uki 5892 0.0 0.0 4016 768 pts/0 S+ 04:22 0:00 grep --color=auto -i dm
With that output you can figure out which one is your DM and then you can kill the process,
but before it log out of your desktop, then type ctrl+atl+f1 to drop to the console and then
you will kill the process, in doubt use again the command to find it again.
The ID is the number right after the word root.
to kill the process type: kill (idnumber)
Repeat the ps aux line to make sure DM and X are not running.
Now you can do the steps:
You will get output if the file is generated
Once you get this done copy(cp command) the generated file named xorg.conf.new which is the video config file to /etc/x11 directory, note it will lose the .new
sudo cp xorg.conf.new /etc/X11/xorg.conf
At this point reboot and see what happen.
This might not work yet and if not then:
This is to find out which packages for nvidia you have installed,
dkpg -l | grep nvidia
if you don't have the nvidia-settings and nvidia-96 then install those.
sudo apt-get install nvidia-settings nvidia-96
Now you will find the nvidia-settings in one of the menus(System/Adminstration or Applications), look if you have more resolutions options.
Lets see what happen.