I got a LinkSprite DiamonsBack Wifi card for Arduino a few weeks ago and it took some time to get it up and running, mainly due to things that I should have known beforehand.

There are a few guides on the internet on setting up the card. Here are some of them that I read:

http://arduino.cc/forum/index.php?topic=67248.0
http://www.linksprite.com/product/showproduct.php?lang=en&id=74

For more details, please refer to original: http://coffeesmudge.blogspot.com/2013/02/setting-up-arduino-wifi-diamondback-card.html