Yesterday I had the same problem again, this time because of a failing DVD-ROM drive which was doing a lot of I/O errors. Removing that line from fstab solved the problem.
Also the emergency console is broken. Sometimes you can enter commands even though the login prompt is shown. Sometimes it takes on character at a time, and when you've entered your whole command char by char you can CTRL+D and execute the buffer. I guess one failed secondary device shouldn't render the whole system unbootable, systemd should be more fault tolerant --
