Recently, I changed my OS kernel from 10.04 to 11.10 (bugs), but after doing it, the video driver for the 8400 GS disappeared (was there in 10.04). I worked out the same procedure I did to install it in 10.04, mainly,

sudo apt-get --purge remove nvidia-current
sudo apt-get --purge autoremove
sudo add-apt-repository ppa:ubuntu-x-swat/x-updates
sudo apt-get update
sudo apt-get -y install nvidia-current

but it didn't work even though the commands seemed to install the driver without problems. Right now my machine is working with the standard drivers, as shown.

williepabon@WP-WrkStation:~$ sudo lshw -C display
[sudo] password for williepabon: 
  *-display               
       description: VGA compatible controller
       product: nVidia Corporation
       vendor: nVidia Corporation
       physical id: 0
       bus info: pci@0000:05:00.0
       version: a2
       width: 64 bits
       clock: 33MHz
       capabilities: pm msi pciexpress bus_master cap_list rom
       configuration: driver=nouveau latency=0
       resources: irq:16 memory:de000000-deffffff memory:c0000000-cfffffff memory:d0000000-d1ffffff ioport:cc80(size=128) memory:dfc00000-dfc7ffff

Any suggestions to correct the problem? Thanks