Comment 6 for bug 1414707

I too have this issue with a fresh vivid installation. In my case this isn't a virtual machine. Booting with the default options, logging into Gnome Shell from gdm, and bam, the screen is locked instantly. Lock screen flickers and gives authentication error.

I bypassed this problem by going into tty and restarting gdm (sudo service gdm restart). Second login attempt doesn't lock the session instantly. I can also confirm that by selecting the systemd boot option the issue doesn't persist.

There's something in dmesg when booting without systemd, but with systemd the following dmesg output doesn't exist:

dmesg |grep logind

[ 6.988059] systemd-logind[1754]: Watching system buttons on /dev/input/event1 (Power Button)
[ 6.988085] systemd-logind[1754]: Watching system buttons on /dev/input/event0 (Power Button)
[ 6.988095] systemd-logind[1754]: New seat seat0.
[ 6.990545] systemd-logind[1754]: Failed to start user service: Unknown unit: user@120.service
[ 6.992441] systemd-logind[1754]: New session c1 of user gdm.
[ 21.103729] systemd-logind[1754]: Failed to start user service: Unknown unit: user@1000.service
[ 21.105989] systemd-logind[1754]: New session c2 of user myusername.
[ 56.858239] systemd-logind[1754]: Removed session c1.
[ 63.669131] systemd-logind[1754]: New session c3 of user gdm.
[ 70.428732] systemd-logind[1754]: New session c4 of user myusername.

[ 56.858239] systemd-logind[1754]: Removed session c1. <- this is the output when restarting gdm from tty.

Hopefully this helps a little bit.