No wired or wireless networking available on Ubuntu 12.04 (wired work from LiveUSB)
Additional Drivers sometimes offers to install the wrong drivers! Please open a terminal and do:
sudo apt-get remove --purge bcmwl-kernel-source
sudo modprobe b44
Now your ethernet should be working. Hook it up and do:
sudo apt-get install linux-firmware-nonfree
Upon reboot, both should be working fine.