I've installed Ubuntu 12.04 this weekend and have had problems getting Unity3d to work with my triple monitor set-up.

I've installed the latest nVidia drivers for my 2 nVidia video cards and have used NVIDIA X Server Settings to configure everything. If I stick each monitor on a separate X screen, all but the primary X screen will appear white and the cursor will be a black X. I can start a terminal on this screen but cannot drag other windows to it. If I kill the "Nautilus" process, the white background disappears and I see my desktop background, but my cursor is still an X and I still cannot drag windows to it.

If I enable TwinView, I can get one screen on two monitors to work properly, but the white screen remains on my third monitor. In addition, I don't like using TwinView because my full-screen applications get stretched.

My current solution is to "Enable Xinerama", use all separate X screens and revert to Unity2d.

I'd love a solution to this as Ubuntu 12.10 is not planned to support Unity-2d and prefer the aesthetics of 3d anyways. I can provide Xorg.conf for all configurations and any other suggested diagnostic information. Below is my closest-to-working xorg.conf:

# nvidia-settings: X configuration file generated by nvidia-settings
# nvidia-settings:  version 295.33  (buildd@zirconium)  Fri Mar 30 13:38:49 UTC 2012

Section "ServerLayout"
    Identifier     "Layout0"
    Screen      0  "Screen0" RightOf "Screen2"
    Screen      1  "Screen1" RightOf "Screen0"
    Screen      2  "Screen2" 0 0
    InputDevice    "Keyboard0" "CoreKeyboard"
    InputDevice    "Mouse0" "CorePointer"
    Option         "Xinerama" "1"
EndSection

Section "Files"
EndSection

Section "InputDevice"
    Identifier     "Mouse0"
    Driver         "mouse"
    Option         "Protocol" "auto"
    Option         "Device" "/dev/psaux"
    Option         "Emulate3Buttons" "no"
    Option         "ZAxisMapping" "4 5"
EndSection

Section "InputDevice"
    Identifier     "Keyboard0"
    Driver         "kbd"
EndSection

Section "Monitor"
    Identifier     "Monitor0"
    VendorName     "Unknown"
    ModelName      "Microvitec PLC MV191"
    HorizSync       30.0 - 81.0
    VertRefresh     56.0 - 75.0
    Option         "DPMS"
EndSection

Section "Monitor"
    Identifier     "Monitor1"
    VendorName     "Unknown"
    ModelName      "CRT-1"
    HorizSync       28.0 - 55.0
    VertRefresh     43.0 - 72.0
    Option         "DPMS"
EndSection

Section "Monitor"
    Identifier     "Monitor2"
    VendorName     "Unknown"
    ModelName      "Microvitec PLC MV191"
    HorizSync       30.0 - 81.0
    VertRefresh     56.0 - 75.0
    Option         "DPMS"
EndSection

Section "Monitor"
    Identifier     "Monitor3"
    VendorName     "Unknown"
    ModelName      "Microvitec PLC MV191"
    HorizSync       30.0 - 81.0
    VertRefresh     56.0 - 75.0
EndSection

Section "Device"
    Identifier     "Device0"
    Driver         "nvidia"
    VendorName     "NVIDIA Corporation"
    BoardName      "GeForce GTS 450"
    BusID          "PCI:1:0:0"
    Screen          0
EndSection

Section "Device"
    Identifier     "Device1"
    Driver         "nvidia"
    VendorName     "NVIDIA Corporation"
    BoardName      "GeForce 9500 GT"
    BusID          "PCI:2:0:0"
EndSection

Section "Device"
    Identifier     "Device2"
    Driver         "nvidia"
    VendorName     "NVIDIA Corporation"
    BoardName      "GeForce GTS 450"
    BusID          "PCI:1:0:0"
    Screen          1
EndSection

Section "Device"
    Identifier     "Device3"
    Driver         "nvidia"
    VendorName     "NVIDIA Corporation"
    BoardName      "GeForce GTS 450"
    BusID          "PCI:1:0:0"
    Screen          2
EndSection

Section "Screen"
    Identifier     "Screen0"
    Device         "Device0"
    Monitor        "Monitor0"
    DefaultDepth    24
    Option         "TwinView" "0"
    Option         "metamodes" "DFP-0: 1280x1024_75 +0+0; DFP-0: 1280x1024 +0+0"
    SubSection     "Display"
        Depth       24
    EndSubSection
EndSection

Section "Screen"
    Identifier     "Screen1"
    Device         "Device1"
    Monitor        "Monitor1"
    DefaultDepth    24
    Option         "TwinView" "0"
    Option         "metamodes" "nvidia-auto-select +0+0"
    SubSection     "Display"
        Depth       24
    EndSubSection
EndSection

Section "Screen"
    Identifier     "Screen2"
    Device         "Device2"
    Monitor        "Monitor2"
    DefaultDepth    24
    Option         "TwinView" "0"
    Option         "metamodes" "DFP-2: 1280x1024_75 +0+0; DFP-2: nvidia-auto-select +0+0"
    SubSection     "Display"
        Depth       24
    EndSubSection
EndSection

Section "Screen"
    Identifier     "Screen3"
    Device         "Device3"
    Monitor        "Monitor3"
    DefaultDepth    24
    Option         "TwinView" "0"
    Option         "metamodes" "DFP-2: nvidia-auto-select +0+0"
    SubSection     "Display"
        Depth       24
    EndSubSection
EndSection

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

Other people have had similar issues. I haven't been successful at any of the few suggestions submitted. Can not get Dual Monitors to work on Different GPUs http://askubuntu.com/questions/30412/3-monitors-with-2-video-cards-not-working?rq=1 How to get second display to work alongside primary display? http://askubuntu.com/questions/148007/multiple-monitors-only-work-with-unity-2d/201086#201086 xorg.conf and Unity3D?