Error found while loading /home/[username]/.profile
In terminal...
gedit .profile
change this:
mesg n || true
to this:
tty -s && mesg n || true
The .profile for the root account may require a similar (but slightly different) fix.
stty -ixon on .profile
I had that command on my .profile, and it was causing the problem in Ubuntu 17.10.
I had put it there because of the recommendations on this question: https://unix.stackexchange.com/questions/12107/how-to-unfreeze-after-accidentally-pressing-ctrl-s-in-a-terminal