Broadcom wifi devices are a problem, and a very popular problem as it turns out. It is a problem that can be resoloved fairly easily with a program named "ndiswrapper" plus your Windows driver files (both the .inf and the .sys).
Step one is to find out the exact chipset version - usually 4306 or 4318, but there are many others. To do this in Linux, open a terminal and enter:
This should list the specific Broadcom chip being used.
Step 2 is to do a search here in Linuxquestions. It's been covered pretty well.
Step 3 come back with other questions, comments, or the solution that helped you to get on the 'net