Got it to work. I was lucky to backup my Ubuntu xorg.conf file before loading Mint 12. I was running an older nVidia driver at the time (270.29). I've replaced all the content of my current MInt xorg.conf with the following and it just works (note you might have to change some of the configuration settings to accomodate your system) :
# start of xorg.conf
# nvidia-xconfig: X configuration file generated by nvidia-xconfig
# nvidia-xconfig: version 270.41.06 (
buildmeister@swio-display-x86-rhel47-08.nvidia.com) Mon Apr 18 15:14:00 PDT 2011
# nvidia-settings: X configuration file generated by nvidia-settings
# nvidia-settings: version 270.29 (buildd@allspice) Fri Feb 25 14:42:07 UTC 2011
Section "ServerLayout"
Identifier "Layout0"
Screen 0 "Screen0" 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 "Acer AL2216W"
HorizSync 30.0 - 82.0
VertRefresh 56.0 - 76.0
Option "DPMS"
EndSection
Section "Device"
Identifier "Device0"
Driver "nvidia"
VendorName "NVIDIA Corporation"
BoardName "GeForce GTX 460M"
EndSection
Section "Screen"
Identifier "Screen0"
Device "Device0"
Monitor "Monitor0"
DefaultDepth 24
Option "TwinView" "1"
Option "TwinViewXineramaInfoOrder" "DFP-0"
Option "metamodes" "CRT: nvidia-auto-select +1920+0, DFP: nvidia-auto-select +0+0"
Option "RegistryDwords" "PowerMizerEnable=0x1; PerfLevelSrc=0x2222; PowerMizerDefault=0x2; PowerMizerDefaultAC=0x1"
Option "NoLogo" "True"
SubSection "Display"
Depth 24
EndSubSection
EndSection
# end of xorg.conf