My Mac desktop computer won't accept blank CDs?

I'm trying to make a mix CD but everytime I insert a blank CD it just sits in the drive for a while then just ejects itself? But when I insert CDs with music and things already on it, the CD loads like its supposed to. Also, when I insert blank DVDs it accepts them just fine. I checked a million times if there was already a disk in there and there's not, so that's not the problem. I don't know what else it could be, help???