OK, an update, for all those who shall follow...
The CTRL-ATL-F1 tip actually worked wonders. For reasons I cannot fathom, hitting that key combo once did nothing to interrupt the evil cycle of X attempting to start. However, getting angry and hitting CTRL-ALT-F1 repeatedly, and most importantly, with a lot of force caused the cycling to stop, and an box appeared telling me that try as it might, it couldn't get X to start. Knowledge is power.
Anyways, after asking for more info and stuff, I read through a error log where it stated (among other things) that:
"Could not init font path element unix/:7100, removing from list!
Fatal server error:
Could not open default font 'fixed'
Please consult
http://wiki.X.Org for help
Please also check the log file "/var/log/Xorg.0.log for additional info"
So, armed with an error message, I attacked the internet.
I found that for some reason, my FontPath variable in the XOrg config file had changed to that unix:7100 thing, and I had to change it back to its default:
FontPath "/usr/11R6/lib/X11/fonts"
instead of
FontPath "unix/:7100"
Since I was still in the tty, I simply used vi to do this:
$vi /etc/X11/xorg.conf
Magically, $startx now worked! I didn't actually have to mess with the runlevels (init 3), but that would have been a necessary next step if keyboard shortcut didn't work.
Afterwards, when I tried logging in with my normal user accounts, I found out that my entire / partition was full, and there was no room left to write the the authorization file - I got the message "GDM could not write to your authorization file. This could mean that you are out of disk space or that your home directory could not be opened for writing. In any case, it is not possible to log in. Please contact your system administrator."
Fortunately I was able to download a copy of
xdiskusage to tell me what was eating up all the space, and I was able to delete unecessary things and solve the GDM problem.
Abadee-Abadee That's All, Folks! Thanks for the tip, xpromisex.