I just installed Ubuntu 12.04 by cd. Unity 3D will not work now only 2D It worked fine in 11.10 and also when I upgraded to the beta of 12.04 through update manager. I tried both Nvidia Proprietary Drivers on the list with no luck. I had many more driver choices in 11.10 and 12.04 beta but the default installed driver always worked before this install. I get a black screen and the wall paper sometimes shows for a few seconds and then goes back to the black screen using Unity 3D.
You may be affected by Bug #982485 if Unity 3D was working on the Beta, but isn't working now. It looks like it is affecting Geforce 6*** and Geforce 7*** cards. Nvidia is aware of the bug, so hopefully there will be a fix rolled out soon.
If you want Unity 3D to work in the meantime, try to add the Ubuntu-X Updates PPA and downgrade the nvidia-current package to 295.33.
(tip for GUI users: use Ctrl+Alt+F1 to get to a text mode login, then type in your login/password at the command line interface to get to a place where you can issue the following commands)
sudo add-apt-repository ppa:ubuntu-x-swat/x-updates sudo apt-get update sudo apt-get install nvidia-current=295.33-0ubuntu1~precise~xup1
There was a security bug in 295.33 so you have to factor this into your decision about whether or not to downgrade.
You will have to uncheck the
nvidia-currentpackage from the Update Manager when you upgrade your system to prevent it from re-installing version 295.40.
Whether or not you downgrade your nvidia driver, watch the bug listing (or subscribe to it) to know when the bug gets fixed so you can upgrade your driver then.