My 08 does it too! It's definitly plastic. I just took a closer look and found what I think to be the problem. Bend down and look up into the fairing in the front above the fender (like you were looking up some skirt...lol). Surrounding the Y at the front brake fluid line junction is a black plastic sheild in place that looks as if it is supposed to protect the steel line coming down from the master cylinder. If you tap that piece of plastic it will rattle against the steel line and make a very distinct rattle. Everything else on my bike seems fine except for the squeeking of plastics when the fairing is manipulated (not the problem). I will install a little round adhiesive rubber bumper pad on the plastic and between the steel line. I think I have some laying around from some cabinets I recently bought. I'll report the results on next ride.