Forza Motorsport 4 Disc Error

I have LT 3.0 and Forza.Motorsport.4.PAL.XBOX360-COMPLEX.
I did:
1. abgx360
2. Burn with ImgBurn, choose Calculate Optimal and Truncate.
Game freeze or get error “Disk not readable” while complete some races or freeze at loading.
When i install game to HDD, it says “”Disk not authorized”.
Answer #1
Burn it again. Maybe you can use another software aside from ImgBurn.