I've had a similar experience. See http://www.ubuntuforums.org/showthread.php?p=2166540&posted=1#post2166540
I'm using a WPA encrypted network, and when I used the version 4 firmware under network manager, the machine locks up and needs a hard reset. However, when I *don't* use NM and configure wpa_supplicant by hand, it works ok. Attached is the part of /var/log/syslog when NM and bcm43xx are getting upset. You can see it attempts to associate with an AP with MAC address 00:00:00:00:00. Which doesn't make any sense. ** Attachment added: "/var/log/syslog" http://librarian.launchpad.net/6453985/crash.txt -- Broadcom bcm43xx broken with 2.6.20.8 kernel https://launchpad.net/bugs/85099 -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs