I've found a way to get the drivers to compile... I just downloaded the intrepid restricted modules package source from Ubuntu.
Then unpack, go to ubuntu-intrepid-lrm/ubuntu-restricted/broadcom
and make -C /lib/modules/`uname -r`/build M=`pwd`
They only work with TKIP for me, at least not with WPA2. (The open source b43 drivers does.)