Some special flags are required to make Compiz work correctly with dual monitors on Fedora 13. I managed to abuse an old config file to get this:
# nvidia-settings: X configuration file generated by nvidia-settings
# nvidia-settings: version 256.35 (This email address is being protected from spambots. You need JavaScript enabled to view it.) Sat Jul 10 11:49:29 EDT 2010
# Xorg configuration created by livna-config-display
Section "ServerLayout"
Identifier "Default Layout"
Screen 0 "Screen0" 0 0
InputDevice "Keyboard0" "CoreKeyboard"
InputDevice "Mouse0" "CorePointer"
Option "Xinerama" "0"
EndSection
Section "Files"
ModulePath "/usr/lib64/xorg/modules/extensions/nvidia"
ModulePath "/usr/lib64/xorg/modules"
EndSection
Section "ServerFlags"
Option "AIGLX" "on"
Option "Xinerama" "0"
EndSection
Section "InputDevice"
# generated from data in "/etc/sysconfig/keyboard"
Identifier "Keyboard0"
Driver "kbd"
Option "XkbLayout" "us"
Option "XkbModel" "pc105"
EndSection
Section "InputDevice"
# generated from default
Identifier "Mouse0"
Driver "mouse"
Option "Protocol" "auto"
Option "Device" "/dev/input/mice"
Option "Emulate3Buttons" "no"
Option "ZAxisMapping" "4 5"
EndSection
Section "Monitor"
Identifier "Monitor0"
VendorName "Unknown"
ModelName "LG W2252"
HorizSync 28.0 - 83.0
VertRefresh 56.0 - 75.0
EndSection
Section "Device"
Identifier "Videocard0"
Driver "nvidia"
VendorName "NVIDIA Corporation"
BoardName "GeForce 8600M GT"
Option "AddARGBGLXVisuals" "True"
EndSection
Section "Screen"
Identifier "Screen0"
Device "Device0"
Monitor "Monitor0"
DefaultDepth 24
Option "TwinView" "1"
Option "TwinViewXineramaInfoOrder" "DFP-1"
Option "metamodes" "CRT: nvidia-auto-select +1680+0, DFP-1: 1680x1050 +0+0"
SubSection "Display"
Depth 24
EndSubSection
EndSection
Section "Extensions"
Option "Composite" "Enable"
EndSection