Comment 2 for bug 1419017

I ran into this problem also, after replacing a GTX 260 with a GTX 960. For me the sequence that resolved this was:

- purge existing nvidia drivers
- add xorg-edgers ppa
- install nvidia-346 drivers & reboot

After this the login screen was in the right resolution, but logging in still didn't display the unity panel. So at a terminal:

- export DISPLAY=:0; ccsm

In ccsm I re-enabled the unity modules, using another ubuntu system as a reference. It looked like *everything* had gotten de-selected. Then one last step:

- rm ~/.config/dconf/user

After that, unity was back.