i followed the these instructions:
STA - No Internet access
If you do not have any other means of Internet access on your
computer, you can install the bcmwl-kernel-source package from the
restricted folder under ../pool/restricted/b/bcmwl on the Ubuntu
install media.
Note: The bcmwl-kernel-source package depends on the linux-headers
packages so you may need to first retrieve the appropriate package(s)
from the online repositories. A running LiveCD/LiveUSB environment has
these packages (allowing the wireless to work), but an installed
system may not. Make sure you have the linux-headers package that
matches your current kernel version, plus the appropriate generic
header packages so that they are automatically updated on a kernel
upgrade. To find out your current kernel use the command:
uname -r
To find what linux-headers packages you have installed use the
command:
dpkg -l | grep headers
Systems installed from CDROM can add the install CD as a package
source and install bcmwl-kernel-source using apt-get as above.
However, if you want to do it manually then the instructions are as
follows:
Navigate the install media and install the packages listed below by
double clicking OR install the packages consecutively from a Terminal
(in the commands below the install media is mounted at /cdrom, but
yours maybe different):
../pool/main/d/dkms
cd /cdrom/pool/main/d/dkms
sudo dpkg -i dkms*
../pool/main/p/patch
cd /cdrom/pool/main/p/patch
sudo dpkg -i patch*
../pool/main/f/fakeroot
cd /cdrom/pool/main/f/fakeroot
sudo dpkg -i fakeroot*
../pool/restricted/b/bcmwl
cd /cdrom/pool/restricted/b/bcmwl
sudo dpkg -i bcmwl-kernel-source*
taken from the official ubuntu help page:
https://help.ubuntu.com/community/WifiDocs/Driver/bcm43xx#STA_-_No_Internet_access
and after a restart wifi was working fine.
sudo lshw -C network
on the command line. Please edit your question to show us that output.