I believe that that board uses a serial backpack for its I2C interface and it is that board with which you are attempting to communicate.
See if this thread helps, make sure you read it all the way through: --> http://arduino.cc/forum/index.php/topic,106655.0.html
Don
[EDIT]: Here's another one --> http://arduino.cc/forum/index.php/topic,128635.0.html