My Xbox 360 or My Game IS Messing up Please help?

I have Just Purchased Grand theft auto 4 for X-box 360 and i played it for about a half hour then it said "disc is unreadable" and it kept saying that. the disc and the tray are perfectly clean. because my other games work just not that one. and ive tried cleaning it each time i don't know what to do please help me.