Bsrgvty

Occasionally my lock screen does this:

That makes logging in difficult. Restarting Unity kind of works, sometimes only a reboot will fix it. My video card is a Sapphire Radeon HD 6870 with dual displays using the open drivers.

Reloading unity restores the password input on the login screen for me (Ubuntu 14.04 with a Nvidia GPU).

1. Switch to an alternate terminal using Ctrl+Alt+F1.



2. 
   

   Reload unity with:

   
   
   

   nohup unity --replace &
   

   
   



3. Switch back to your graphical terminal using Ctrl+Alt+F7. You may have to wait several seconds if you see a black screen.

Unity sort of works after this but you can at least save your work in progress:

• The compiz grid plugin seems to think multiple monitors are now a single monitor.




• The global menu bar no longer works.




• Menus in window title bars no longer work (if enabled).




• Custom global keyboard shortcuts don't work.

I had the same problem on an HP with Radeon 6370 graphics. I'm still using open source graphics, but I'm using the versions that came from the oibaf repository - they are a little 'edgier' than the stock open source, but not as edgy as xorg-edgers.

sudo add-apt-repository ppa:oibaf/graphics-drivers
sudo apt-get update
sudo apt-get upgrade

installs the drivers

sudo apt-get install ppa-purge
sudo ppa-purge ppa:oibaf/graphics-drivers

removes the drivers.

open terminal

CTRL+ALT+F3

reset the unity

$ unity-reset
$ setsid unity 

if that didnt workout try to re-install the unity & the desktop

$ sudo apt-get autoremove ubuntu-desktop 
$ sudo apt-get autoremove unity 
$ sudo apt-get update 
$ sudo apt-get install unity
$ sudo apt-get install unity-2d 
$ sudo apt-get install ubuntu-desktop 
$ sudo shutdown -r

now install the ati driver

$ sudo add-apt-repository ppa:ubuntu-x-swat/x-updates
$ sudo apt-get update
$ sudo apt-get install fglrx gksu
$ sudo amdconfig --initial && sudo shutdown -r

after the reboot
u can run the driver buy ALT + F2

copy & past this

gksu amdcccle

This can be worked around without losing your session by:

1. Switch to a tty (e.g. Ctrl+Alt+F1)


2. Log in


3. Run: sudo loginctl unlock-sessions
   


4. Switch back to the Desktop: Ctrl+Alt+F7 (or F8).

From the bug report fori this issue and this answer to a similar question