Hey Dusty,
I'm having a similar issue currently with my portable player (Sirius S50) and my car radio (The standard RES model - No Sirius/DVD). I don't lose the speakers, but I am getting the buzzing. It just seems like the connector doesn't properly fit into the aux jack on the front of the radio, and if it moves out of alignment just slightly it starts buzzing. I haven't had time to take my vehicle in to tell them about this (and the other issues I'm having), so I've just been using the FM transmitter built into the Sirius radio..
Sorry I couldn't be more helpful, but at least you're not alone. :beerchug: