My Macbook Pro hangs and freeze screen. I was hoping that it is an antivirus that I can remove. I have Norton for Mac on my computer. I know that I have to maybe check my RAM also. Now, I have run the Antivirus several times and it continues to freeze where I am not able to click on the screen. Can someone help me determine what is going on? I cannot find my restore disc. I have never had this problem until I upgrade my operating system to Yosemite.