Probably just a scratch on the disk. Try cleaning with dish soap and warm water. If that fails, you could try SkipDr
http://www.heartlandamerica.com/browse/item.asp?PIN=123026&DL=GAW1&SC=WIG20001&
DVD/CD drives are not all the same. You could try another drive; sometimes one will read through scratches better than another.
Good Luck