I just got a Dell 2407 1920x1200 display. It took me a while to get it
working at 1920x1200, the Nvidia control panel was only supporting up to
1280x1024. The Fedora Core 6 Display control panel went to 1680x1050 but
that was with the nv driver. The trick is to add the following to the
Device section,

Option "ModeValidation" "NoMaxPClkCheck"

I think I found that on one of the Nvidia forums, it's not original to me.
BTW the card I'm using is an FX 5700 with 256M of RAM and the Nvidia
1.0.9742 beta driver. One more note, XP can't run this card at 1920x1200,
it's limited to 1680x1050 because there is no way to disable the max pixel
clock check in XP.

For the benefit of others here is my xorg.conf file. In addition to
supporting 1920x1200 this file also does everything you need to get the 3D
effects running on FC6 (BTW don't bother turning them on, they are worse
than useless).

# Xorg configuration created by system-config-display

Section "ServerLayout"
Identifier "single head configuration"
Screen 0 "Screen0" 0 0
InputDevice "Mouse0" "CorePointer"
InputDevice "Keyboard0" "CoreKeyboard"
EndSection

Section "Files"
EndSection

Section "Module"
Load "glx"
Load "v4l"
Load "extmod"
Load "dbe"
Load "fbdevhw"
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 "InputDevice"
Identifier "Keyboard0"
Driver "kbd"
Option "XkbModel" "pc105"
Option "XkbLayout" "us"
EndSection

Section "Monitor"

### Comment all HorizSync and VertSync values to use DDC:
Identifier "Monitor0"
ModelName "Dell 2407"
### Comment all HorizSync and VertSync values to use DDC:
HorizSync 31.5 - 90.0
VertRefresh 59.9 - 60.1
ModeLine "1920x1200" 154.0 1920 1968 2000 2080 1200 1203 1209 1235
Option "dpms"
EndSection

Section "Device"
Identifier "Videocard0"
Driver "nvidia"
Option "ModeValidation" "NoMaxPClkCheck"
EndSection

Section "DRI"
Group 0
Mode 0666
EndSection

Section "Screen"
Identifier "Screen0"
Device "Videocard0"
Monitor "Monitor0"
DefaultDepth 24
Option "AddARGBGLXVisuals" "True"
Option "DisableGLXRootClipping" "True"
SubSection "Display"
Depth 1
Modes "1920x1200" "1650x1080" "1280x1024" "1024x768" "800x600" "640x480"
EndSubSection
SubSection "Display"
Depth 4
Modes "1920x1200" "1650x1080" "1280x1024" "1024x768" "800x600" "640x480"
EndSubSection
SubSection "Display"
Depth 8
Modes "1920x1200" "1650x1080" "1280x1024" "1024x768" "800x600" "640x480"
EndSubSection
SubSection "Display"
Depth 15
Modes "1920x1200" "1650x1080" "1280x1024" "1024x768" "800x600" "640x480"
EndSubSection
SubSection "Display"
Depth 16
Modes "1920x1200" "1650x1080" "1280x1024" "1024x768" "800x600" "640x480"
EndSubSection
SubSection "Display"
Depth 24
EndSubSection
EndSection

Section "Extensions"
Option "Composite" "Enable"
EndSection