Display Settings tool does not set monitor or video card (Fedora 12) [closed]

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How can I get Gnome to display at a resolution higher than 640x480, using a video card and monitor that support a higher resolution?

Here is what I have tried so far:

From the menu bar, I select System->Administration->Display. A window asks me for the root password. I enter the root password and a window titled "Display Settings" appears.

The button to the right of "Resolution" shows 640x480. Clicking anywhere on this button brings up a menu that gives me choices of only 640x480 or 320x240.

I select the Hardware tab. It shows Monitor Type: Unknown, Video Card: Unknown video card.

I click Configure to the right of "Monitor", a "Monitor" window comes up. I find my monitor in the list (it is a Dell 1905FP, using the digital input), select it, click OK. The Display Settings window shows Monitor Type: Dell 1905FP (Digital).

Now I click Configure to the right of Video Card. A "Video Card" window comes up. I select the line "nv - ... QUADRO cards" since I have a QUADRO card. I click OK. The Display Settings window now shows ... "Video Card: Unknown video card"! What happened to the choice that I just selected?

Now I click OK on the Display Settings window, thinking that at least I can set the monitor type. A window appears with this message:

Display settings changed

You need to log out and restart the X server for the changes to take effect.
Configuration was written to /etc/X11/xorg.conf, original configuration saved as /etc/X11/xorg.conf.backup.

I click OK again and the window closes. But when I look in the file /etc/X11/xorg.conf, it says, it has these lines (after other lines about other things):

Section "Monitor"
        Identifier "Monitor0"
        VendorName "Unknown"
        ModelName "Unknown"

ls -l indicates that this file was modified at the time I closed Display Settings, but I find no evidence that my monitor type was saved anywhere in this file. And indeed when I log out and restart the computer, and bring up Display Settings again, it says Monitor Type: Unknown again.

I can edit the file directly, of course, but my experience trying that was very bad (the system rebooted with no usable graphics at all, and I had to use single-user mode to restore the xorg.conf file before I could boot normally again).

According to System Monitor, my computer has Fedora Release 12 (Constantine), kernel Linux 2.6.32.16-150.fc12.x86_64, GNOME 2.28.2.