problem backing up some ps2 games

[cmdrtrew]

I"ve tried to backup a few ps2 games using nero V5.5.10, some go fine, others not at all. Not at all were slycooper, nhl 2003 by 989 sports, and Drakan, the ancients gate. The error message was "blank or invalid media". The drive is a dvd/cd-rw combo so it reads it fine if i just want to look on the files on the disk as a dvd, but nero will not write or save an image file. I followed the normal, recommended settings that are around different sites but nothing. Any suggestions? tks