My laptop screen (MacBook Pro - new in Apr of 2011) froze up. The cursor moved but individual windows (or buttons or links) did not respond.
I had shut the system down holding down the on/off hardware button.
On restart, I got the apple startup screen where the screen, the apple and the pinwheel animation all had horizontal stripes across the length of the screen.
It labored there for awhile then the screen went black and the fan started to rev up like crazy.
again I had to shut down the system the same way.
I usually keep all my software up to date. I am noticfied automatically, but generally choose to update the system. I am not sure what version of Mountain Lion I have. The last thing I updated was iTunes earlier this week.
Since a simple restart does not handle this I am fearful I have sacrificed yet another hard drive to the gods...
I do have backup dirtives but i manually backup only wark I want backeup so I do not think I have a mirrored system on any of the drives...