No such problem with my NEC 3500A with fw 2.18 and 8X Yuden000 T02. 4X, 8X, 12X, and 16X...all okay. I did see similar rings with my RicohJpn W11 4X +RW media when I do several partial burns. However, when I rewrite the entire disc with a DVD movie, then I no longer see the ring.
It looks like the dye is not reacting very well with a change in write speed? Try a quality high-end media.