Macbook Random Shutdown

Hi;
It’s been five weeks without my macbook suffering from RSS. It’s been sent back to Apple Canada twice. The first time, they told me that nothing was wrong with the computer. The second time, they told me that it is the music sharing programs on the computer that are causing the problem. Hence, music is dangerous according to them!! I also have experienced extreme overheating and rapid battery loss, but they continue to tell me that there is nothing wrong with the computer. I will be asking for a refund for the cost of the computer. This computer was purchased in September from Apple Canada and I have only used it for 4 months, considering the fact that it has been gone for the last five weeks.