Comment 13 for bug 114490

I also have this problem (only noticed it in Gutsy, but FGLRX hasn't let me suspend since Dapper or Edgy)... I can sometimes fix it with:

sudo killall `ps aux | grep ipw3945d | grep -v grep | awk '{print $11}'`
sudo rm /var/run/ipw3945*.pid
sudo rm /var/run/dhclient.eth1.pid
sudo rmmod ipw3945

sleep 2

sudo modprobe ipw3945
sudo /etc/init.d/dbus restart

If that doesn't work, I try rmmod ipw3945, /etc/init.d/dbus stop, hit the wireless kill switch (Fn+F2 on my Inspiron), then bring ipw3945 and dbus back up.

It's pretty annoying... a proper fix would be nice.