Up until now this machine has been flawless aside from a harddrive failure last year, at which point I replaced it with an SSD. However over the last month or so it has been crashing on a regular basis (sometimes multiple times in a day). The screen freezes aside from the mouse, and no amount of time or attempts to force quit will help so I have to manually restart. Sometimes while my computer is in sleep it will just randomly reboot. It's not the end of the world since I mostly work in Photoshop which can recover work. But it is very annoying. Any ideas what could be going on? I was hoping to wait until the next iMac Retina update before upgrading my machine.