Terabytes: unable to supply whole message for now. This is a full screen error message which in part is saying there was "a serious system error". Instructions to restart system, and some sort of timer/counter near bottom of screen counting off a "physical memory dump" in progress. Not knowing what is going on, I simply restart system promptly since I'm not knowledgeable about this "physical memory dumping" process, or how much time I have to try and read the whole screen. I can say that the two times this has happened, it has been on startup. I will try to read more of screen if it comes up again.
Thank you for the info about it possibly saying what file crashed.