I have the same problem. I tried to install the nvidia oficial driver from nvidia page after that, and in /var/log/Xorg.0.conf NVIDIA say that the driver is not compatible with the ABI 9.0 from Xorg.
The problem is after the update from xserver-xorg-core 2:1.9.99.901+git20110131.be3be758-0ubuntu1.
I have the same problem. I tried to install the nvidia oficial driver from nvidia page after that, and in /var/log/ Xorg.0. conf NVIDIA say that the driver is not compatible with the ABI 9.0 from Xorg.
The problem is after the update from xserver-xorg-core 2:1.9.99. 901+git20110131 .be3be758- 0ubuntu1.
now runing wih nouveau..., without opengl.