Re: Problems with Asus monitor
"I imagined that the monitor is a purely passive peripheral. Maybe the problem was with driver software, but this too is surprising, as I certainly didn't install any drivers"
Have you ever looked at the Xorg logs? They contain the make and model of your screen along with resolution, dpi, pixel ratio, refresh rates etc. Now I don't claim to know what's going on at the low level inside the drivers of Linux or any other OS but obviously there is a data exchange between the screen and GFX driver then some driver config magic to display your desktop at the ideal resolution. It may be that the logic in the screen was re-setting/crashing and sending incorrect or corrupt data back to the computer and the OS/driver was failing to cope with it.
I am, of course, assuming you meant that you were running Ubuntu in a GUI mode and not booting direct to console, which I'd imaging could never cause an OS crash no matter what the screen logic did.