Sounds like you might have a ground loop. Try playing a cassette with the lights on and see if you still get the buzzing noise. If you do, you have a bad ground connection somewhere. If your stereo is quiet with a cassette playing and the lights on, I'd check the antenna as in the previous post.

Also, have their been any aftermarket mods done to the stereo? Any amps, speakers, etc. added?

__________________
Chris
2007 E550 4Matic - 61,000 Km - Iridium Silver, black leather, Sport package, Premium 2 package
2007 GL450 4Matic - 62,000 Km - Obsidian Black Metallic, black leather, all options
1998 E430 - sold
1989 300E - 333,000 Km - sold
1977 280E - sold
1971 250 - retired

"And a frign hat. They gave me a hat at the annual benefits meeting. I said. how does this benefit me. I dont have anything from the company.. So they gave me a hat." - TheDon