Thanks for the help! I played around a bit today, and now I have a working GNOME desktop. Now I just need to switch to KDE... here's what I did today. On nVidia's website, they have a list of all the options that can be thrown into xorg.conf. Two of those deal with specifying monitor types. I used:
Option "Connected Monitor" "DFP"
to specify monitor type. I also noticed in my /var/log/Xorg.0.log that the nVidia driver was complaining about not being able to connect to the ACPI Event Daemon. I then installed it (acpid) by following Hlinger's instructions
here. This didn't solve my problem, but the nVidia driver did stop complaining about ACPI Events. Also, I'm in the process of turning this computer into a multiseat setup, so I have two graphics boards, monitors, etc. When I installed the OS, I had X automatically generate an xorg.conf. It recognized both graphics boards and monitors, but only generated one screen setup. Today I edited it to add in the extra screen. I then added the new screen to the ServerLayout section. My server layout now looks like:
Section "ServerLayout"
Identifier "single head configuration"
Screen 0 "Screen0" 0 0
# I added Screen1-didn't touch anything else
Screen 1 "Screen1" 0 0
InputDevice "Mouse0" "CorePointer"
InputDevice "Keyboard0" "CoreKeyboard"
Option "DontZap" "false"
EndSection
After this edit, when I run startx GNOME comes up just fine. ( I did install XFCE, but I had installed GNOME earlier. Not sure why the XFCE install didn't reconfigure the desktop started with startx.)
I have attached Xorg.0.log(I had to rename it to Xorg.0.log.txt) and xorg.conf,
Thank you very much to everyone who has helped me on this problem.