I'm kinda curious about this also. I was having issues with some CD-Rs, and a couple of games, after I did my pot adjustments, I can load regular games fine, but no CDRs.
BTW, in your alls experiance, what is better, a Taiyo 80min or an MAM-A (which I hear are just as good) 74 min? I figure a 74 minute disc is easier for the Duo to read, but am a bit unsure, as they are harder to find.