Comment 54 for bug 1315369

I also tried the suggested workaround from comment #50 (with the Trusty kernel) and ran into the same problem. This time after screen locked, I had black external monitor, working laptop screen but without the login prompt, and no recognised keyboard input - I.e,. I couldn't event ctrl-alt-F1 to get to login prompt. I'll attach the logs below just in case they help.