I was using the Broadcom STA proprietary wireless driver but decided to give the B43 wireless driver a go. At first it didn't work but after I did "sudo modprobe b43" it worked perfectly... for awhile. Now, using the B43 driver, I can see networks but I can't connect to them. Also, when I switch back to the STA driver I can't see any networks at all.

I'm using Ubuntu 10.10 and my computer specifications are in my signature