This question already has an answer here:
How to Install Broadcom / STA Wireless card (BCM43XX)
My previous question about this issue had been closed, and I had been directed to this link. I read through it all day, but none of the solutions over there helped. I still can't even switch the wireless adapter on. The only working wireless module is Bluetooth. I know for a fact that the wireless adapter is not faulty, because after having asked this question, I installed Windows and it worked flawlessly. I just decided to give Ubuntu another shot.
Here's the story: on my Dell Inspiron N4050, I upgraded from the preinstalled 10.10 to 11.04 then 11.10. Then I installed the proprietary driver through Additional Drivers. Since then, the wireless card just stopped working completely, and won't even switch on. Not even a clean, fresh installation of 12.04 fixed it.
So what now? Should I take it in for warranty replacement?
Here's the relevant output of
09:00.0 Network controller: Broadcom Corporation Device 4365 (rev 01)