Starting with lower intensity (11) stopped things from crashing completely-- looks like explorer is dead and there were some display artifacts, but I'm still here typing this message. But also, hash rate on one card went down to 4kh/s. Increasing its intensity to 13 inside cgminer made things more crashy. Going to reboot and try some other settings, though it's hard to know if anything worked until after I run it for many hours.

Thanks again for the suggestions! Worst comes to worst, I can manage stuff from within cgminer and never quit out as long as when I go down to intensity 8, it doesn't interfere with my work (gamedev, so using 3d accel).