It's a common annoyance with many plasma TVs. If this is that bothersome, I'd consider returning it ASAP and research more about today's TVs and re-consider LCDs.
I hear a slight buzzing/humming sound from my tv on bright/white images. I have turned down the contrast and brightness and this seemed to help some. Is this normal? I have a 4 yr old Panasonic 50in thx plasma that does not make this noise.