Comment 242 for bug 1311316

=/ I'm also facing this issue. The curious part is that the issue happens more if I take a while to reboot the machine. I mean, if I don't reboot and just put the machine to sleep this issue start to happens more and more. I also realized that when I use two different users in the machine it also implies to happen more.
Sometimes just type ctrl+alt+f7 a couple of times works to bring the entry field back, but not always (as today), though, typing unity --replace in the user I had the GUI start it works. Last time I have this issue I was with two users logged in, so I just pkill -9 -u <user2> and the login entry screens backs to user1. Also happens to the login screen stay black just with the mouse pointer working.