[CentOS] Widescreen monitor won't configure to a wide screen

I just put a 1680x1050 LCD monitor on my home system, and I went into
system-config-display to configure it as such, and it just won't take.

I had to tweak some of the settings by hand, but when I log out, I get
the wide screen for both the Nvidia driver splash screen and the login
screen.

But, when I log in, It jumps back to 1280x1024 and refuses to run in
wide screen mode.

Here's the xorg.conf (even when I'm logged in and the screen is only 1280x1024):

# Xorg configuration created by system-config-display

Section "ServerLayout"
        Identifier     "single head configuration"
        Screen      0  "Screen0" 0 0
        InputDevice    "Keyboard0" "CoreKeyboard"
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:
#       HorizSync    31.5 - 65.5
#       VertRefresh  56.0 - 65.0
#       Option      "dpms"
        Identifier   "Monitor0"
        ModelName    "LCD Panel 1680x1050"
 ### Comment all HorizSync and VertSync values to use DDC:
        HorizSync    30.0 - 82.0
        VertRefresh  56.0 - 76.0
EndSection

Section "Device"
        Identifier  "Videocard0"
        Driver      "nvidia"
EndSection

Section "Screen"
        Identifier "Screen0"
        Device     "Videocard0"
        Monitor    "Monitor0"
        DefaultDepth     24
        Option      "NoRenderExtension" "False"
        Option      "AllowGLXWithComposite" "True"
        Option      "RandRRotation" "True"
        Option      "XvmcUsesTextures" "True"
        Option      "AddARGBGLXVisuals" "True"
        Option      "TripleBuffer" "True"
        Option      "DamageEvents" "True"
        SubSection "Display"
#               Modes    "1680x1050" "1600x1024" "1440x900"
"1400x1050" "1280x1024" "1280x960" "1280x800" "1152x864" "1024x768"
"800x600" "640x480"
                Viewport   0 0
                Depth     24
                Modes    "1680x1050" "1600x1200" "1600x1024"
"1440x900" "1400x1050" "1280x1024" "1280x960" "1280x800" "1152x864"
"1024x768" "800x600" "640x480"
        EndSubSection
EndSection

The commented out Horix and Vert syncs are for my old monitor (a 17"
non-ws), and the new ones are from the manual for the new screen.  I
tried with these commented out, but it still would not work.

One thing I noticed is that when the gdm starts up, it goes from "auto
adjust" (wide screen) to "analog-d" (non-ws) - dunno what that means.

Any suggestions?  It's really annoying to have a wide screen and not
be able to use it....

Thanks.

mhr


What am I missing?