It was at the end of a demo to a cow-orker, the current playlist (before the demo started) was also RioDJ generated.

I remember paying with the equaliser (changed it to parametric and changed a few values then cancelled those changes) plus we had been in and out of a lot of menus, I certainly couldn't tell you what to do to reproduce it, but if it happens again I will take more notice and try to narrow it down.