you need to add b43 to the /etc/modules file.
you'll have to do it as root.
so in a terminal type this
when gedit come up navigate to /etc/modules
and add b43 to the list.
it will then be started on boot up.
also if you had sta driver install b43 may have been blacklist and thus ignored at boot up.
you can check to see if it is blacklisted by
navigating to /etc/modprobe.d/blacklist and seeing if it's there if it is remove it or place a # infront of it and that should do it.