On your Ubuntu live media, you have the firmware cutter package, which you can use on a Broadcom Windows driver (bcmwl5.sys) from the wireless card install CD-ROM.
The location of b43-fwcutter package is:
copy it to your home directory off the distribution media.
Install the b43-fwcutter package, and you should have the b43-fwcutter program installed in
/usr/bin for you to run. (If you can manage to get a wired connection, you will be offered the option to just download the appropriate Broadcom driver to run through the fwcutter).
Run it on the Windows driver bcmwl5.sys file, probably in an empty directory to make copying the .fw files easier. The b43-fwcutter will "cut" out all the firmware files needed from the Broadcom driver. Copy all the .fw files into
/lib/firmware/b43, and you should see network-manager pick up the card. Use
sudo mkdir /lib/firmware/b43 and
sudo cp *.fw /lib/firmware/b43 to move the files.
This firmware is all that the b43 driver needs to run on your 4311 chip. Since you haven't been connected to the Internet, you probably didn't manage to install any Broadcom drivers which would blacklist the b43 driver, so it should run automatically as soon as the firmware is supplied. Reboot if necessary to see the available wireless access points.