I have an LG DVD recorder that I use to record TV shows on to keep. So far all of the finalized DVDs work fine on my iMac until last night. I put in a DVD that is the same brand (TDK DVD-R) as all the others and the iMac tried to read it but it ended up just spitting it out. I then put it in my DVD player for my TV and it worked fine. I then copied that DVD onto another brand new DVD using my LG and another DVD player to make a fresh copy just to see if the original DVD was scratched or something. No go. Why does the iMac spit out just this one DVD and a brand new copy of that same DVD but it accepts all other DVDs just fine?? It is an iMac 2.4GHz 20 inch about a month old.