Comment 4 for bug 874872

Exact same behaviour for me resulting from same upgrade to 11.10.

Lightdm remains unresponsive after password input. Can select other user from lightdm screen, which removes the password box and does not allow login (tty8)

Can switch back to tty7 and log back in

sudo service lightdm restart: fails due to upstream job status
sudo service lightdm halt: fails as well
sudo kill -9 (job ID): returns no error and job disappears
sudo service lightdm start: returns no error. returns jobID, but lightdm does not appear in sudo ps -A
sudo start lightdm: returns no error. returns jobID, but lightdm does not appear in sudo ps -A

at this point other terminals are inaccessible

logout kills the desktop manager, but desktop items remain, and folders can be openned with no decoration, like old xdm

ctrl-alt-del sends shutdown signal and tty1 returns