Nvidia has released a new driver for Linux that comprises a lot of bug fixes. Here are the list of bugs that have been fixed:
To update your current Nvidia driver under Ubuntu 11.04, launch the Terminal and run these commands:
sudo apt-add-repository ppa:ubuntu-x-swat/x-updates
sudo apt-get update
sudo apt-get install nvidia-current
You can check later your current Nvidia driver version via the NVIDIA X Server Settings window to make sure the latest driver is properly installed:
Also applicable for Ubuntu 11.10.