A quick scanning of forum showed
1. User community sticks with ethernet LAN based shield
2. Seven out of 10 user have problem running Wifi shield
3. Eight out of 10 run into issue upgrading the firmware
4. Nine out of 10 need to use Arduno 1.0.2 (not the latest IDE) to get WiFi working
5. We still can't get static IP address to work! even after firmware update.
We too have a "AT32UC3A1512" but issued command successfully.
batchisp.exe -device AT32UC3A1256 -hardware usb -operation erase f memory flash blankcheck loadbuffer c:/wifi_dnld.elf program verify start reset 0http://www.binarytaskforce.com/Weblog/2013/09/21/arduino-wifi-firmware-update/
Hope this helps, Team BTF