I think people are misleading you here in telling you it's the dimmer fix... I had the exact same problem on my player. - it went back to cambridge and said it was the dimmer problem, and claimed it was fixed... As soon as I got back, there it was again. I bet there are lines of lighter and darker parts of the display when it's having issues?

Anyways, to fix it, try reflashing a whole rio image... That fixed it for me, at least.

Matthew