Comment 23 for bug 660596

Same problem with nvidia NVS 450 with 3 monitors. I got it to work intermittently with only one monitor connect with similar to comment #10 but slightly more newbie-proof:

Close any open application.

If in X, you need to kill and and switch to a text terminal with the following:
open a terminal
sudo stop gdm
Ctrl-Alt-F2

Cleanup to start fresh:
sudo apt-get remove --purge nvidia-* xserver-xorg-video-nv xserver-xorg-video-nouveau
sudo echo "blacklist nouveau" >> /etc/modprobe.d/blacklist.conf

Install specific nvidia drivers:
curl -OL http://us.download.nvidia.com/XFree86/Linux-x86_64/256.53/NVIDIA-Linux-x86_64-256.53.run
sudo bash ./NVIDIA-Linux-x86-256.53.run
-> it needs to succeed.

Force a boot flag:
sudo nano /etc/default/grub
-> change the line to the following: GRUB_CMDLINE_LINUX_DEFAULT="quiet splash nomodeset"
sudo update-grub

You can now reboot:
sudo shutdown -r now

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In the meantime I'll put back the video card into my windows box and NX into my linux machine :(