I have experienced it twice yesterday since yosemite DP5. The first one happened when I tried to refresh a safari webpage, the whole screen just frozen and nothing on the screen is functioning (although the mouse cursor was still movable).
The second time happened when I use safari too. And the system just shut down without a warning. I rebooted the computer and all open pages are gone.
The second time happened when I use safari too. And the system just shut down without a warning. I rebooted the computer and all open pages are gone.
