I searched the forums first cause I was almost certain this question would be on here, but I didn't see any! All of the sudden my mac pro wont read blank CD-R's and blank DVD-R's. It will read burned disc and software just fine. I was burning with these same disc fine a few days ago. I get this "This disc cannot be used because it is not recognized." I tried rebooting with no luck! The only thing that I've done to my Mac lately is add a 1 TB External HD (Western Digital) to my mac through the 800 plug. My boss is coming over soon to pick up some disc. Any help would be swell!