My late 2013, 27" iMac is completely up to date with software, but keeps randomly having complete system wide freezes (yes, usually when Safari is open). Today it froze, I crashed it and rebooted, but it's still frozen. I tried rebooting in safe mode. Nothing. Last time this happened I found something that recommended disconnecting peripherals and then reconnecting at some point, and it worked like a charm, but I can't find the information anymore. I have a usb keyboard, Bluetooth mouse. Have tried rebooting and connecting everything one-by-one, but still not working. PLEASE HELP!!!