Woooo... totally freaked me out. I just updated Rebooted and then screen just blacked out. I was thinking.. CRAP!!!! then it comes back on. I thought ok... that's odd... click on Firefox.. BOOM blacked out again. It came back on in about the same amount of time compare to the first one. Then so far it is fine and never happened again. I am afraid to reboot but I will do it after I send this out. Was that normal or it only happened to mine? My iMac is new bought a week ago. It would suck if I have to take it back so soon... LOL