I have a the iMac 27" 2010 with whatever the last update was. After that update, I get white screen with loading bar then Black screen with mouse icon parked in the upper left corner only then Mouse disappears. Hard drive sound is it's working. Already tried to start in restore mode planning to use timemachine on airport, but it won't populate, so no luck. Tried safe mode. Aftrrer white screen it goes back to the black screen and hangs, so no luck either. Tried to reset SMC & PRAM. no change. Any help? I'm desperate.