thats probably because dma is disabled on your optical drive....
read what i said in that post, so once you find what device your dvd is (if you don't already know) then issue that command and see....i am going to say it is set to 0, so do what is said to enable it..you can also check if the IO_support is set to 32bit by using "hdparm -c" and to enable if it is not, use -c1 ...the same is true with this command but use "c" instead of "d" as the argument...