Try sudo apt-get purge nvidia replace nvidia by the driver you are using. It will use the free driver Nouveau.
That worked for me.
Try this:
sudo apt-get update
sudo apt-get install --reinstall ubuntu-desktop
Doesn't boot after fresh install
Try sudo apt-get purge nvidia replace nvidia by the driver you are using. It will use the free driver Nouveau.
That worked for me.
Try this:
sudo apt-get update
sudo apt-get install --reinstall ubuntu-desktop