Just wanted to let you know that the error was not with my config nor the ubb program, but rather with the server I was installing it on. Apparently, it was misconfigured. In fact, we now can't see our home page, but hey, the ubb works! So Marysa, and anyone else pulling your hair out over this, DOUBLE check with your webhost that it's not a problem on their end. I had to make three requests for them to check before they caught the problem.
Thanks to Hal and Jacob for their assistance. Have a great day!
