Random Unpredicatable Crash on Desktop and Menu Slowdown on Laptop

I am running on a desktop PC, quad core AMD 16gb ram, nvidia gtx750ti

Sometimes after just a minute, sometimes after 15 minutes or up to an hour or two the game totally crashes and either displays a solid colour screen or switches to a black screen with the TV displaying a note of “no signal” or “unsupported mode”

when it crashes in this way, I can’t alt-tab or ctrl-alt-delete to return to desktop, have to manually shut-off the PC

I am playing the game on my display’s native resolution 1366 x 768. it plays beautifully before crashing

EDIT: It also happens if I play the game windowed at a lower resolution.

Meanwhile, if I try to play on my laptop (which is dual core with 8gb ram) the game plays pretty smooth at lower resolution, except for the menus/character select which are painfully slow