I don't know how all of this started, but I think I'm still dealing with issues that I posted in the thread:

http://ubuntuforums.org/showthread.php?t=703998

The basic gist of it was that I was having user Groups problems, was unable to see several menu buttons like the Synaptic Package Manager, and I fixed this by running:
usermod -a -G admin userNameHere

This solved some of my access problems. I was, however, having a problem with no sound that I reported here:

http://ubuntuforums.org/showthread.php?t=792090 and was advised to add myself to the Sound group under the User Privileges tab of the Users and Group editor.

When I went to this tab- I found it empty for both myself and root. I don't know why this was, but I clicked on OK to leave this window, and I think that by doing so I inadvertently wiped out the groups that were there originally. After rebooting I get a bunch of ugly terminal output and no Ubuntu login window.

I tried repeating the usermod command and I now get the message:

The GDM group "gdm" does not exist. Please correct GDM configuration and restart GDM.

And I am redirected to the shell. Where should I go from here? If I type in groups for myself, I see only: root.

Thanks!