Same problem
I have a similar problem. Some DVDs containing videos are not read under Snow Leopard - they get ejected, whereas the Boot camp Windows OS reads the same discs fine, so there cannot be anything physically wrong with the drive. I am unable to get to an Apple store because I live in Crete Greece. Apple have no official presence here other than third party resellers.
I have to sort this problem out myself via internet research.
I am using a 15 month old Macbook Pro.
Dave
(I know there is a kind of Apple store in Athens on the Greek mainland but it is virtually a one man business and of no practical use for this kind of problem. A genius bar to them is a place where clever people go for a drink under the Acropolis)