I just bought a new Imac about a week ago, and I've been really amazed by it. since my last computer was a 13" macbook from 2007. But about twice a day, It will freeze up. I've left it for about thirty minutes, but I eventually I have to shut it down and restart it. It doesn't seem to matter what I'm doing when it happens, It's happened when I'm browsing Itunes or google chrome. and playing very simple 8-bit games? OH and I've cleaned it with onyX, but it's still freezing up.