Same issue with my 2007 2.16 C2D MB. Bought the disk at BB today, tried to install it and got to about 15 minutes in when the MB restarted, the DVD was ejected and the computer continued to boot up into 10.5.8. Called Apple, told it sounded like a bad disk and to exchange it at BB. If I still had trouble to call them back. Guess I am off to BB tomorrow.
I guess with 5 mil disks made a few were bound to be bad. Frustrating, but not the end of the world. My MB still boots up, so that's a plus!