My Dell device had come with a pre installed version of Ubuntu 11.10, after a upgrade to long term support Ubuntu 12.04, my WIFI and blue tooth stopped working all together. After trying failing for many times I had almost given up on WIFI all together, until i stumbled up on a Ask Ubuntu answer by the awesome user izx, who has modified some drives to make the device work. So here are the steps to install the modified drivers, open a new terminal and fire away.
1. Remove the default Broadcom drivers.
sudo apt-get remove bcmwl-kernel-source
2. Install the prerequisite packages.
sudo apt-get install linux-headers$(uname -r | grep -Po "\-[a-z].*") sudo apt-get install build-essential dkms
4. Install using dpkg.
sudo dpkg -i <name of the package>
5.After the install restart your machine. open a terminal and type
rfkill unblock all
You should be able to use your WIFI now cheers 🙂