I've recently had some issues with my wireless. Ubuntu is detecting the wifi card and the kernel module is loaded and I can even turn the wifi on and off from the menu up in the top right (this is in gnome shell, but the behavior is the same in Unity). However, I can't get a single wifi network to show up and I can't connect to any wifi network by manually entering the SSID.
If I boot into OS X, the wifi works fine.
Here's what I have from iwconfig:
wlan0 IEEE 802.11bg ESSID:off/any Mode:Managed Access Point: Not-Associated Tx-Power=20 dBm Retry long limit:7 RTS thr:off Fragment thr:off Power Management:off
03:00.0 Network controller: Broadcom Corporation BCM4331 802.11a/b/g/n (rev 02)
I'm not sure what other info might be needed. I haven't tried a whole lot since I haven't seen these particular symptoms anywhere else. I have restarted the laptop numerous times, logged out and in, reloaded the kernel module (b43) all to no avail.