I dont see a monitor section. i would guess thats your problem. I would add a little more info to the xorg.conf file. you might try this one but make a backup first before changing it.
Code:
Section "ServerLayout"
Identifier "Default Layout"
Screen 0 "Screen0" 0 0
InputDevice "Keyboard0" "CoreKeyboard"
EndSection
Section "InputDevice"
Identifier "Keyboard0"
Driver "kbd"
Option "XkbModel" "pc105"
Option "XkbLayout" "us"
EndSection
Section "Device"
Identifier "Videocard0"
Driver "nv"
Busid "PCI:01:00.0"
EndSection
Section "Screen"
Identifier "Screen0"
Device "Videocard0"
Monitor "Monitor0"
EndSection
Section "Monitor"
Identifier "Monitor0"
EndSection
Give that a try. if it does not work check the log in /var/log/Xorg.0.log and post any lines that start with (EE).