Step 1: Ensure your console is properly cooled. Needs to be free of dust and roaches, and should have plenty of room for airflow. If it's in a cabinet, pull it out. This game will tax your hardware more than any other on the console.
Step 2: Do some research on the MD5 issue. You will find several helpful tips to prevent the crash, and to prevent loss of data if it happens. There are quite a number of threads here with the information on it.