It's been a while since I installed mine, but I don't think I had to change anything in the bios. But you could always disable anything related to wireless access, whether in bios, or in the windows hardware manager. I would try that first.
Unfortunately, the next thing to do is to open the computer again and check the seating of the Broadcom card. It sounds like a problem with the installation, or perhaps you have a bad card. Can you double check that the card is inserted correctly, no bad pins/connector, or pieces of dirt blocking anything? Did you secure the Broadcom card with a screw?
If it appears there was a problem with the installation then fix that, button it up again, and try it again.
Otherwise you have to decide whether to remove the Broadcom card, and exchange it or leave it out.