iwlagn: Microcode SW error detected. Restarting 0x82000000.

If you have gotten the above error in your syslog, you probably are not able to connect to wireless APs that require WPA passphrases, but can connect to ones that require WEP or no security. While searching for solutions, there were some that offered solutions for controlling the power of the card (for temperature-related issues), but those did not address my issue. Fortunately, the solution was fairly simple for my problem. I have Ubuntu Jaunty, with the 2.6.28-15 kernel. The resolution came when I looked in synaptic at the installed linux-restricted-modules and found I had two instances from older kernels still installed. Purging those completely from the system, and retrying to connect to my WPA2-enabled AP succeeded. Give it a shot.