Warning! Danger Will Robinson!
If you have an NVidia card older than and including the G80 GPU, including the 6, 7, and 8800 series cards, DO NOT UPDATE TO Ubuntu 12.04 Precise yet! The latest NVidia driver installed with 12.04, 295.40, will not work with Compiz and 3D Unity. Precise will run in Unity 2D mode, but not 3D. I’ll write more of the details in a subsequent post.
I didn’t know this and spent 7 hours last night troubleshooting the collection of issues until I stumbled upon the NVidia forum post.
If you really cannot wait to update Ubuntu to their new long-term support release, you can download the previous 295.33 nvidia driver and install it from its script file after uninstalling 295.40 in a recovery text console before you boot 12.04 LTS Precise into a 3D mode. You can download the 295.33 driver here.
In order to install the 295.33 driver, enter a console either through the recovery boot or better, booting into Ubuntu 2D and then holding Ctrl-Alt-F2 down together. Log into the resultant terminal screen, then type:
sudo service lightdm stop
sudo service lightdm status
The latter should either say the service wasn’t found or that it is stopped. The bottom line is that the OpenGL/GLX framework isn’t being used. Then uninstall the core NVidia packages with:
sudo apt-get purge nvidia-current nvidia-current-updates
Then execute the 295.33 script from the directory to which you downloaded it:
sudo sh NVIDIA-Linux-x86_64-295.33.run
Follow the prompts to the end, then reboot/restart:
After that, Ubuntu 12.04 LTS Precise Pangolin should work fine in with 3D support. Worked for me.