15.04 Vivid Vervet won't boot after uninstalling lightdm

We've been trying to figure out how to disable the login screen on 15.04 Vivid Vervet. Our method of doing this on 14.04 was to uninstall lightdm. If we do this on 15.04, however, the system won't boot. :( The main error seems to be: "Failed to isolate default target, freezing." (I have a picture of this, if there is a way to upload one.)

I'm not sure if this is a bug or just new behavior, but someone on a forum suggested I report it. Also, if anyone has any advice for getting rid of the login screen, I'm all ears. I tried this and it didn't work: http://askubuntu.com/questions/16371/how-do-i-disable-x-at-boot-time-so-that-the-system-boots-in-text-mode/79698#79698