Comment 79 for bug 732677

Had issues with the natty version of the driver, since switching on/off via Fn-F6 (Dell) did not work, driver did not come up again (but after reboot + right timing of Fn-F6 during reboot). rmmod/modprobe did not reenable wireless.

Finally resolved my issues with the not fully funcional driver by installing and pinning the old 5.60 driver from maverick http://packages.ubuntu.com/maverick/i386/bcmwl-kernel-source/download
and additionally setting power management
iwconfig eth1 power off
to resolve steady disconnection/connetion problem [1]

This iwconfig has to be issued after switching off/on wireless, and these solutions did not work:
http://ubuntuforums.org/showthread.php?t=1597874

so I set up a 1 minute cron job to do this for me:
# m h dom mon dow command
* * * * * /sbin/iwconfig eth1 power off

Well, that seems to work (although a heavy weight solution).
Hm, will wait with upgrade to Ubuntu 11.10 then, if it breaks this.

[1]
Aug 31 19:53:39 ubuntubox wpa_supplicant[1013]: CTRL-EVENT-DISCONNECTED bssid=00:16:9d:44:c0:40 reason=0
Aug 31 19:53:39 ubuntubox NetworkManager[865]: <info> (eth1): supplicant connection state: associating -> disconnected
Aug 31 19:53:40 ubuntubox wpa_supplicant[1013]: Associated with xx:xx:xx:xx:xx:xx
Aug 31 19:53:40 ubuntubox wpa_supplicant[1013]: CTRL-EVENT-CONNECTED - Connection to xx:xx:xx:xx:xx:xx completed (reauth) [id=0 id_str=]
Aug 31 19:53:40 ubuntubox NetworkManager[865]: <info> (eth1): supplicant connection state: disconnected -> associated
Aug 31 19:53:40 ubuntubox NetworkManager[865]: <info> (eth1): supplicant connection state: associated -> completed
Aug 31 19:53:43 ubuntubox NetworkManager[865]: <info> (eth1): roamed from BSSID (none) ((none)) to xx:xx:xx:xx:xx:xx (MYESSID)
Aug 31 19:53:50 ubuntubox wpa_supplicant[1013]: CTRL-EVENT-DISCONNECTED bssid=xx:xx:xx:xx:xx:xx reason=0
Aug 31 19:53:50 ubuntubox NetworkManager[865]: <info> (eth1): supplicant connection state: completed -> disconnected
Aug 31 19:53:50 ubuntubox NetworkManager[865]: <info> (eth1): supplicant connection state: disconnected -> scanning

P.S: Broadcom, somebody of you reading this? Try to fix your driver stuff, please.