I have a fresh install of 11.04 (reformatted etc) and I am having problems with a 3rd monitor. I'm running 2 video cards and the default NVidia drivers. I let the drivers generate my xorg.conf because still somewhat a n00b :)
I have no issue with the 2 working monitors. They are setup as TwinView which may or may not be best but I would prefer to avoid running Xinerama because I fear I would no longer be able to use Unity. Long story short, no known issues with the 2 monitors that are on the same video card.
The 3rd monitor appears to have no window manager. I have no launch bar, no panels and when I right click -> new file gedit opens and there are no File / Edit / Tools ... options, nor is the title bar visible (with close, minimize, maximize). If I try to write anything in the text editor, it writes the text to one of the other, working, screens (Almost as if the window on the 3rd monitor never receives focus). My xorg.conf file is posted below -- please let me know of any other files that would be helpful. I really appreciate any advice!
# nvidia-settings: X configuration file generated by nvidia-settings
# nvidia-settings: version 270.29 (buildd@roseapple) Fri Feb 25 14:43:24 UTC 2011
Section "ServerLayout"
Identifier "Layout0"
Screen 0 "Screen0" RightOf "Screen1"
Screen 1 "Screen1" 0 0
InputDevice "Keyboard0" "CoreKeyboard"
InputDevice "Mouse0" "CorePointer"
Option "Xinerama" "0"
EndSection
Section "Files"
EndSection
Section "InputDevice"
# generated from default
Identifier "Mouse0"
Driver "mouse"
Option "Protocol" "auto"
Option "Device" "/dev/psaux"
Option "Emulate3Buttons" "no"
Option "ZAxisMapping" "4 5"
EndSection
Section "InputDevice"
# generated from default
Identifier "Keyboard0"
Driver "kbd"
EndSection
Section "Monitor"
# HorizSync source: edid, VertRefresh source: edid
Identifier "Monitor0"
VendorName "Unknown"
ModelName "ProView/EMC/PTS"
HorizSync 30.0 - 80.0
VertRefresh 60.0 - 75.0
Option "DPMS"
EndSection
Section "Monitor"
# HorizSync source: edid, VertRefresh source: edid
Identifier "Monitor1"
VendorName "Unknown"
ModelName "DELL E1910H"
HorizSync 30.0 - 83.0
VertRefresh 56.0 - 75.0
Option "DPMS"
EndSection
Section "Device"
Identifier "Device0"
Driver "nvidia"
VendorName "NVIDIA Corporation"
BoardName "GeForce 9400 GT"
BusID "PCI:1:0:0"
EndSection
Section "Device"
Identifier "Device1"
Driver "nvidia"
VendorName "NVIDIA Corporation"
BoardName "GeForce 8400 GS"
BusID "PCI:5:0:0"
EndSection
Section "Screen"
Identifier "Screen0"
Device "Device0"
Monitor "Monitor0"
DefaultDepth 24
Option "TwinView" "1"
Option "TwinViewXineramaInfoOrder" "CRT-0"
Option "metamodes" "CRT-0: nvidia-auto-select +0+0, CRT-1: nvidia-auto-select +1280+0"
SubSection "Display"
Depth 24
EndSubSection
EndSection
Section "Screen"
Identifier "Screen1"
Device "Device1"
Monitor "Monitor1"
DefaultDepth 24
Option "TwinView" "0"
Option "TwinViewXineramaInfoOrder" "CRT-0"
Option "metamodes" "nvidia-auto-select +0+0; 1366x768 +0+0"
SubSection "Display"
Depth 24
EndSubSection
EndSection