fillipos is right.
It would seem that you don't have a 1:1 copy with your burner and Nero. Your buerner is capable of reading/burning the 2353 bytes of RAW data but not the 96 bytes of sub-channel data containing any copy protection that the game might have.
The ideal PS2 game reader/burner has the DO-RAW+96 capability as identified in
www.elbe.de Supported Writers table. Acer burners are generally incompatible.