Are you talking about the buzz that sounds like a transformer up on a telephone/electric pole? If so, my dealership told me that all Kawasaki's that have vented rotors have this noise to some degree. My '04 500 LTD didn't start making the noise until ~200 miles. I now have 700 miles and its about 1/2 as loud.
Per the dealer... you can chamfer the pads or the holes in the rotor to eliminate the noise. I cut an angle on my pads with a dremel, but it didn't change anything. There are way to many holes in the rotor to try that method.
Good luck... Since it isn't a safety thing, I'm just ignoring the sound and hoping it goes away eventually.
Brian
P.S. Once I hit 20 MPH (decelerating), the noise stops on my bike. Does it do the same on yours?
P.S.S. I'll try the sandpaper method this weekend, but I'm not too hopeful. I've looked and cleaned the pads with no change, plus I'd expect the vent holes to keep the pads from glazing. Maybe not, though.