It is definitely the USB.

Playing classical MP3's that I ripped at 320Kbps, I get noise the instant I plug the USB cable into the docking station. I don't even have to plug it all the way in.

When I remove the cable, the noise stops immediately.

The Ethernet cable produces no noise.

Now I *really* want to ditch the USB cable. Let's get that Ethernet performace up to snuff, Rio.

Incidentally, though not surprisingly, the sound quality coming out of the RCA jacks is still inferior to the stereo mini sound, to my ears. Anyone concur?