Comment 42 for bug 836250

I noticed the same problem (can't connect to the wireless network after upgrading from 11.04 to 11.10) on Lenovo ThinkPad T500.

Intel Corporation PRO/Wireless 5100 AGN [Shiloh]

The work around disabling n also worked for me:
sudo rmmod iwlagn
sudo echo "options iwlagn 11n_disable=1" > /etc/modprobe.d/disable11n.conf
sudo modprobe iwlagn