Hello everyone,
For those who ran into Arduino wifi shield firmware update issue, we did our own upgrade recently by following the procedure from http://arduino.cc/en/Hacking/WiFiShieldFirmwareUpgrading. It was straight forward and we did this successfully. Passing on the information, we have documented the entire update process with screenshots and output.
http://www.binarytaskforce.com/Weblog/2013/09/21/arduino-wifi-firmware-update/
Hope this helps
Team BTF