I've been running Ubuntu 13.04 for a while now, and everything has been running fine, but now it won't boot past the splash screen. I was using it, shut it down, and when I turned it back on, it would go from the splash screen to a black screen with a cursor at the top left. I ran the boot repair program on the recommended settings and it still doesn't boot after restart.
The problem was with the graphics drivers I downloaded. I went into the recovery console and removed them through the terminal. I needed to use bumblebee to get my graphics card up and running.