C230 Coupe ('03): Buzzing From Sun Roof

I have an '03 C230 Kompressor Coupe. Very pleased with the car, however, has anyone experienced a loud buzz that comes from the wind deflector when the sun roof is open? It begins around 50 mph and it doesn't seem to matter if the side windows are open or closed or whether the A/C is on or off. At first I thought it was a noise coming from the light switch pod, but when I pull on the deflector it seems to lessen the noise. Any ideas?? -Jim