The bcm43xx driver module requires firmware to be installed before it will work correctly. Firmware is not installed by default, so if
you did not install it, it is not installed. Look at the output of this command for any errors:
Also, the bcm43xx driver is no longer used. The b43 driver has replaced it. It is available in newer kernels. (>= 2.6.18) It may not be compiled into the earlier 2.6.18 kernels, but it is available with a re-compile.
http://linuxwireless.org/en/users/Drivers/b43
You did not post your distro version or kernel version. This type of info should be posted when asking for help.