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).
Switch to an alternate terminal using Ctrl+Alt+F1.
Reload unity with:
nohup unity --replace &
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.
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