It's possible that the red laser has burned out. There are separate lasers to read and write CDs (infrared laser) and DVDs (red laser), so if one burns out then that type of disc is no longer usable.
Appreciate the info, I took the drive apart and only saw one laser, but I don't know enough about them to fix it anyway. I went with a Plextor drive because I don;t have SATA capabilities. Roxio software included.