Comment 44 for bug 1424013

I found the black-screen problem on a Lenovo 3000 N100 laptop after doing an update on 14.04 LTS recently (early September 2016). This is a 32-bit machine.

As a workaround I installed flashback:
apt-get install inxi gnome-session-flashback compizconfig-settings-manager

I could then select either of the Gnome options and log in OK (i.e. it works with both Metacity and Compiz, but the normal Ubuntu session fails).

OpenGL renderer string: GeForce Go 7300/PCIe/SSE2

Turning off X11 Sync Objects did not fix it.
I then tried some different drivers using
  System Settings -> Software and Updates -> Additional Drivers
X.Org with Nouveau did not work at all
Nvidia 173 works OK.

Summary: using the older Nvidia 173 driver is an adequate workaround for me, but it looks as if this problem is more complex than just 'Sync Objects'.