NOOOOOO!!!!!!! (might not be able to finish Galaxy)

I dont know how it happened but i started playing after school, in the observatory place i had the option to go to the center of the universe or stay and get more stars. I wanted to get all the stars i could then go but i decided to see what was in the center instead, so i got to the cutscene and it froze and said "Disc could not be read." I tried again but it just kept saying that in the cutscene, i dont know why this happened, there aren't any scratches on the disc either except 1 i think. So i can get all the stars except the ones in the center of the universe. NOOOOOOO!!1!!!1!!one!!! This sucks