Hrmmm. I use memorex media with no problems (I was having tons of problems with philips media, even though I heard it is relabeled memorex. Go figure). Other then wild guessing, I am clueless.
Try http://www.dvdplusrw.org. Some good information as far as hardware compat. there. Some DVD-RW don’t get along well with certain combinations of OS, media, etc.