I am working on an issue with my Ubuntu 13.10 installation. I am attempting to get 4 monitors up and running but I am having some trouble. So far, I installed and updated to the latest NVIDIA drivers (331.20). Initially X would not start (after installation) so I replaced my xorg.conf with xorg.conf.failsafe. This fixed that problem, but then I tried to enable the other 2 monitors (other video card) and xorg fails to start once again (after I login there is no desktop). I am fairly new to linux but I am not a complete beginner, but I'm not comfortable poking around too much on my own to troubleshoot yet....

lspci -nn | grep VGA:

03:00.0 VGA compatible controller [0300]: NVIDIA Corporation GF110 [GeForce GTX 570 Rev. 2] [10de:1086] (rev a1)
05:00.0 VGA compatible controller [0300]: NVIDIA Corporation GF110 [GeForce GTX 580] [10de:1080] (rev a1)

It seems that the nvidia-settings tool does not result in a good xorg.conf file. Here it is:

# nvidia-settings: X configuration file generated by nvidia-settings
# nvidia-settings:  version 331.20  (buildmeister@swio-display-x86-rhel47-05)  Wed Oct 30 18:20:32 PDT 2013

Section "ServerLayout"
    Identifier     "Default Layout"
    Screen      0  "Screen0" 0 0
    Screen      1  "Screen1" RightOf "Screen0"
    InputDevice    "Keyboard0" "CoreKeyboard"
    InputDevice    "Mouse0" "CorePointer"
    Option         "Xinerama" "1"
EndSection
...    
Section "Monitor"
    Identifier     "Configured Monitor"
EndSection

Section "Monitor"
    Identifier     "Monitor0"
    VendorName     "Unknown"
    ModelName      "SHARP HDMI"
    HorizSync       15.0 - 68.0
    VertRefresh     55.0 - 76.0
EndSection

Section "Monitor"
    Identifier     "Monitor1"
    VendorName     "Unknown"
    ModelName      "Samsung SyncMaster"
    HorizSync       0.0 - 0.0
    VertRefresh     0.0
EndSection

Section "Device"
    Identifier     "Configured Video Device"
    Driver         "vesa"
EndSection

Section "Device"
    Identifier     "Device0"
    Driver         "nvidia"
    VendorName     "NVIDIA Corporation"
    BoardName      "GeForce GTX 570"
    BusID          "PCI:3:0:0"
EndSection

Section "Device"
    Identifier     "Device1"
    Driver         "nvidia"
    VendorName     "NVIDIA Corporation"
    BoardName      "GeForce GTX 580"
    BusID          "PCI:5:0:0"
EndSection

Section "Screen"
    Identifier     "Default Screen"
    Device         "Configured Video Device"
    Monitor        "Configured Monitor"
EndSection

Section "Screen"
    Identifier     "Screen0"
    Device         "Device0"
    Monitor        "Monitor0"
    DefaultDepth    24
    Option         "Stereo" "0"
    Option         "nvidiaXineramaInfoOrder" "DFP-1"
    Option         "metamodes" "HDMI-0: nvidia-auto-select +640+0, DVI-I-3: nvidia-auto-select +0+1080"
    Option         "SLI" "Off"
    Option         "MultiGPU" "Off"
    Option         "BaseMosaic" "off"
    SubSection     "Display"
        Depth       24
    EndSubSection
EndSection

Section "Screen"
    Identifier     "Screen1"
    Device         "Device1"
    Monitor        "Monitor1"
    DefaultDepth    24
    Option         "Stereo" "0"
    Option         "metamodes" "DVI-I-2: nvidia-auto-select +0+0"
    Option         "SLI" "Off"
    Option         "MultiGPU" "Off"
    Option         "BaseMosaic" "off"
    SubSection     "Display"
        Depth       24
    EndSubSection
EndSection

Section "Extensions"
    Option         "Composite" "Disable"
EndSection