Try borrowing a different monitor. If that fixes it, it's the monitor.
If it happens with a different monitor, it might be the video card.
I want to say something that might be of interest. At the house where I live I have two boxes using one monitor with a KVM switch -- this is a nice, hardware KVM switch of some kind that someone gave me, and I have confidence that it is "known good".
Okay, the PRIMARY box is running OpenBSD, that is my firewall, but I also have X on there and a browser and so forth. I will use it without fail. The monitor never fails with this box.
Now, I have a SECOND box with the Vector Linux on there. I boot this box up occasionally, to watch videos and so forth (it has more proprietary CRAP software on there to render videos and so forth -- I do not want such things on my firewall).
Now, when this Vector Linux box is running, SOMETIMES the monitor will do this -- it will go black, and the led lights will flicker, in a line, from left to right.
At that point, I kill X, with Ctrl-Alt-Backspace, and start it again, with `startx`. Okay, the window manager starts again, no problem, and away I go.
I say that to say this -- this suggests to me that at least in my case, the problem is NOT with the monitor, as the monitor has never done this while the KVM puts the video output of the Primary box to the monitor.
Regrettably, I have never "switched" the KVM while the problem was happening, as that would be the way to prove this one way or the other.
EDIT -- this monitor is some kind of cathode-ray oldschool monitor, not a flat panel one.
Oh -- and to type with no echo to the screen -- the able martial artist can do this kind of thing, no problem, as we see here!!! Especially the Aikido person -- once they have contact, they know where everything is!