I copied the music off (I'm at the office), formatted and copyied the music back to its original location on the Carbon. It 'Integrated' and 'Finalized'.
Shortly after I finished this I realized that I am truly an idiot and do not deserve to own such a nice toy as the Carbon.
I was interpreting the 'EQ' display (which you can toggle to by pressing the center 'select' button on the D-Pad) as Genre, and it was set to Trance. After the reformat, it reverted to 'EQ Off' and displayed that quite clearly.
I'd set EQ to trance on the ride home after a wedding reception Sunday night (and had the mental state of someone coming from an open-bar event) and completely forgotten about it.
I'll go away and hang my head in shame now.
I just hope this misadventure can make it into the Rio tech support scripts for future reference. I've very thoroughly proven the old axiom: "Make it idiot proof and they'll invent a better idiot."