Extractado de
help.ubuntu.com/comunity: Cita: Old Installs Conflicting
If either of nvidia-glx-legacy/nvidia-glx-new are installed a dotfile is created in /lib/linux-restricted-modules/ . Even after these packages are uninstalled the dotfile will remain and may frustrate efforts to use the nvidia-glx package. See this [WWW] launchpad bug about the hidden file not being removed when nvidia-glx-new is uninstalled (also applies if nvidia-legacy is removed) for details.
Ese manual es un paso a paso oficial... Seguramente te ayude.