Ok im another user who has this problem....  Hardy Heron 8.04 - was working fine - after patches/updates etc... then i enabled "expo" and noticed this-afternoon its not working anymore, i hadn't rebooted either.. or logged-out..  I dont believe twinview is the problem... none the less i will attach my xorg.conf for viewing...


# nvidia-settings: X configuration file generated by nvidia-settings
# nvidia-settings:  version 1.0  (buildmeister@builder62)  Mon May 19 00:30:30 PDT 2008

Section "ServerLayout"
    Identifier     "Layout0"
    Screen      0  "Screen0" 640 0
    Screen      1  "Screen1" 0 0
    Screen      2  "Screen2" RightOf "Screen0"
    InputDevice    "Keyboard0" "CoreKeyboard"
    InputDevice    "Logitech G5" "CorePointer"
EndSection

Section "Files"
    RgbPath         "/usr/lib/X11/rgb"
EndSection

Section "Module"
    Load           "dbe"
    Load           "extmod"
    Load           "type1"
    Load           "freetype"
    Load           "glx"
EndSection

Section "ServerFlags"
    Option         "Xinerama" "0"
EndSection

Section "InputDevice"
Identifier "Logitech G5" 
Driver "evdev"
Option "CorePointer"
Option "Device" "/dev/input/by-id/usb-Logitech_USB_Gaming_Mouse-event-mouse"
Option "ZAxisMapping" "invert"
Option "Emulate3Buttons" "false"
Option "Buttons" "9"
Option "Resolution" "800"
EndSection

Section "InputDevice"
    # generated from default
    Identifier     "Keyboard0"
    Driver         "kbd"
EndSection

Section "Monitor"
    # HorizSync source: edid, VertRefresh source: edid
    Identifier     "Monitor0"
    VendorName     "Unknown"
    ModelName      "Samsung SyncMaster"
    HorizSync       30.0 - 81.0
    VertRefresh     56.0 - 75.0
    Option         "DPMS"
EndSection

Section "Monitor"
    # HorizSync source: xconfig, VertRefresh source: xconfig
    Identifier     "Monitor2"
    VendorName     "Unknown"
    ModelName      "TV-0"
    HorizSync       28.0 - 33.0
    VertRefresh     43.0 - 72.0
    Option         "DPMS"
EndSection

Section "Monitor"
    # HorizSync source: xconfig, VertRefresh source: xconfig
    Identifier     "Monitor1"
    VendorName     "Unknown"
    ModelName      "CRT-1"
    HorizSync       28.0 - 33.0
    VertRefresh     43.0 - 72.0
    Option         "DPMS"
EndSection

Section "Device"
    Identifier     "Videocard0"
    Driver         "nvidia"
    VendorName     "NVIDIA Corporation"
    BoardName      "GeForce 8500 GT"
    BusID          "PCI:3:0:0"
    Screen          0
EndSection

Section "Device"
    Identifier     "Videocard1"
    Driver         "nvidia"
    VendorName     "NVIDIA Corporation"
    BoardName      "GeForce 8500 GT"
    BusID          "PCI:3:0:0"
    Screen          1
EndSection

Section "Device"
    Identifier     "Videocard2"
    Driver         "nvidia"
    VendorName     "NVIDIA Corporation"
    BoardName      "GeForce 8500 GT"
    BusID          "PCI:2:0:0"
    Option         "TVStandard" "PAL-B"
EndSection

Section "Screen"
    Identifier     "Screen0"
    Device         "Videocard0"
    Monitor        "Monitor0"
    DefaultDepth    24
    Option         "TwinView" "0"
    Option         "TwinViewXineramaInfoOrder" "DFP-0"
    Option         "metamodes" "DFP: nvidia-auto-select +0+0"
    SubSection     "Display"
        Depth       24
    EndSubSection
EndSection

Section "Screen"
    Identifier     "Screen2"
    Device         "Videocard1"
    Monitor        "Monitor2"
    DefaultDepth    24
    Option         "TwinView" "0"
    Option         "metamodes" "TV: 640x480 +0+0"
    SubSection     "Display"
        Depth       24
    Option         "TVStandard" "PAL-B"
    EndSubSection
EndSection

Section "Screen"
    Identifier     "Screen1"
    Device         "Videocard2"
    Monitor        "Monitor1"
    DefaultDepth    24
    Option         "TwinView" "1"
    Option         "metamodes" "CRT: 640x480 +0+0, TV: 640x480 +0+0"
    SubSection     "Display"
        Depth       24
    EndSubSection
EndSection