Main problem would be the media. You have to use very high quality media. Also, the speed you burn them at. You can adjust the laser pot, yet i personally dont like doing it, as it shortens the life span of the laser in the long run.
I use traxdata 4x mini's and burn @2x using nero. never have problems with em
head to
www.maxconsole.com and check out the gamecube forums there. There is plenty of info on DRE (disk read error).
HaNz