I found several issues with the same symptoms but every fix I tried didn't work.
I have a Dell XPS15z with a SSD drive (and optimus). I installed ubuntu 12.10 with Bumblebee, and everything was fine.
But, suddenly, ubuntu doesn't start anymore, well, at least lightDM doesn't, but i'm not sure the bug lies in LightDM.
I only get a black screen with the cursor at the top left.
I can access a console by hitting ctrl+alt+f1.
What i've tried so far (with no success):
- restarting lightdm manually (sudo service lightdm restart)
- adding a delay (sleep x) before exec lightdm (racing condition) in the lightdm.conf
- installing GDM
But no way, none of them worked, so maybe my issue is not the same.
The thing is I'd like to work now :p
Does anyone can give me some advice ?
Thank you, Benjamin.