OK, this was what had happened. I was trying to edit some startup scripts so that I could type "ant" in Terminal instead of "/usr/bin/ant/jakarta-1.2.0/bin" to start up ant. I had edited the csh.login script, but it did not work. Then I decided to edit the "rc.common" script in the /etc directory, which is what OS X loads when it starts up. I edited the path, and got what I wanted to work, but created another problem of Terminal not recgonizing commands such as "sudo" or "ls."
So . . . I decided to add another path in the rc.common script, rebooted, and panicked when I saw the "Aqua screen of death" staring back at me. I later realized that what had happened was that by changing the path, OS X could not load the files from the /bin directory, which were critical for the OS to boot.
Thanks to Iromongoose, I was able to put an original copy of rc.common back into the invisible /etc directory in OS 9. (Aside: I never realized how fast my TiBook was in OS 9! Man, my 550 Mhz TiBook running in OS 9 *is* at least as fast as my old PIII 1Ghz Dell.) I rebooted, the OS X window popped up, and I was home free.
This whole ordeal might sound a bit strange, but it was actually not all that complicated. The lessons that I have learned from this experience are mainly: know what those Unix scripts do, know what you are doing when you're editing those scripts, and always make a copy of the original just in case.
I still want to be a Unix power user, but I guess I should hold off on editing those scripts until I get a copy of "Mac OS X Unleashed" in my hands.
