as everyone has said, you can't rule out media as the issue unless you've been recording the MEDIA ID code on each disc that you burn. brands use a number of different manufacturer's and the only way you can say you're using the "same discs" is if they ahve the same media id. and if you're using memorex, the likelihood of you having consistent media ids is VERY slim. memorex is the whore of the dvd world. They outsource their production to wherever it's cheapest this week without regard for quality standards, slap their name on it, and people buy it because it's a "known" brand when in fact, there's nothing known about it since there's no way of telling who manufactured the discs until you actually put them in your computer and check the id.