Computer does not shut down

If you run:

sudo shutdown -h now

Does it turn off?

No, same problem, it goes into the coma.

Hi ,
the title says "Computer does not shutdown" but in description " I have to power it off in order to restart."

What exactly is the problem ? Can shutdown properly the PC from menu ?
or both shutdown and reboot not working ?

Also we want little more info
+++++++++++++++++++++++++++++++++++++
cat /etc/lsb-release && uname -r
lspci -nnk | grep -iA2 vga
cat /var/log/Xorg.0.log | grep -e EE -e WW
+++++++++++++++++++++++++++++++++++++
above are commands you should give in terminal (ctrl+alt+t , to open it) . One line at time . We want the results .

Thank you

The computer turns off the monitor and it seems to go into sleep, but it never finishes it off. It is some kind of coma, it
does not work anymore, but it is still not completely switched off.

Here are the results:

++++++++++++
blackmagic@blackmagic:~$ cat /etc/lsb-release && uname -r
DISTRIB_ID=Ubuntu
DISTRIB_RELEASE=12.04
DISTRIB_CODENAME=precise
DISTRIB_DESCRIPTION="Ubuntu 12.04.1 LTS"
3.2.0-29-generic-pae
+++++++++++++
blackmagic@blackmagic:~$ lspci -nnk | grep -iA2 vga
01:00.0 VGA compatible controller [0300]: NVIDIA Corporation G86 [GeForce 8400M GS] [10de:0427] (rev a1)
 Subsystem: Dell Device [1028:0209]
 Kernel driver in use: nvidia
++++++++++++++
blackmagic@blackmagic:~$ cat /var/log/Xorg.0.log | grep -e EE -e WW
 (WW) warning, (EE) error, (NI) not implemented, (??) unknown.
[ 36.849] (WW) The directory "/usr/share/fonts/X11/cyrillic" does not exist.
[ 36.886] (II) Loading extension MIT-SCREEN-SAVER
[ 40.633] (WW) evdev: Logitech USB Receiver: ignoring absolute axes.
[ 63.251] (II) XKB: reuse xkmfile /var/lib/xkb/server-EE935C823A0CC0BC2AF3100D13C373C636D9742B.xkm
[ 369.243] (II) XKB: reuse xkmfile /var/lib/xkb/server-EE935C823A0CC0BC2AF3100D13C373C636D9742B.xkm
[ 439.424] (II) XKB: reuse xkmfile /var/lib/xkb/server-EE935C823A0CC0BC2AF3100D13C373C636D9742B.xkm
+++++++++++++++

Thanks.

The computer turns off the monitor and it seems to go into sleep, but it never finishes it off. It is some kind of coma, it
does not work anymore, but it is still not completely switched off.

Here are the results:

++++++++++++
blackmagic@blackmagic:~$ cat /etc/lsb-release && uname -r
DISTRIB_ID=Ubuntu
DISTRIB_RELEASE=12.04
DISTRIB_CODENAME=precise
DISTRIB_DESCRIPTION="Ubuntu 12.04.1 LTS"
3.2.0-29-generic-pae
+++++++++++++
blackmagic@blackmagic:~$ lspci -nnk | grep -iA2 vga
01:00.0 VGA compatible controller [0300]: NVIDIA Corporation G86 [GeForce 8400M GS] [10de:0427] (rev a1)
 Subsystem: Dell Device [1028:0209]
 Kernel driver in use: nvidia
++++++++++++++
blackmagic@blackmagic:~$ cat /var/log/Xorg.0.log | grep -e EE -e WW
 (WW) warning, (EE) error, (NI) not implemented, (??) unknown.
[ 36.849] (WW) The directory "/usr/share/fonts/X11/cyrillic" does not exist.
[ 36.886] (II) Loading extension MIT-SCREEN-SAVER
[ 40.633] (WW) evdev: Logitech USB Receiver: ignoring absolute axes.
[ 63.251] (II) XKB: reuse xkmfile /var/lib/xkb/server-EE935C823A0CC0BC2AF3100D13C373C636D9742B.xkm
[ 369.243] (II) XKB: reuse xkmfile /var/lib/xkb/server-EE935C823A0CC0BC2AF3100D13C373C636D9742B.xkm
[ 439.424] (II) XKB: reuse xkmfile /var/lib/xkb/server-EE935C823A0CC0BC2AF3100D13C373C636D9742B.xkm
+++++++++++++++

Thanks.

Sorry , I forgot the asterisk and one more important command

Here are the commands in case you want to uninstall nvidia drivers from terminal

+++++++++++++++++++++++++++++++++
sudo apt-get purge nvidia*
sudo apt-get install ubuntu-desktop
sudo reboot
+++++++++++++++++++++++++++++++++

Thanks NikTh, that solved my question.