i had the same problem on a winbox.
before rendering open the system activity monitor and follow the progress of the charts while rendering. i suppose that the cpu will be a stright line at its maximum (which apparently isnt a good thing:)) and the page file will be constantly growing to the maximum. if so- you just dont have enough memory. yepp, 'I used to render the same model before without problem'. me too. just changed some properties of transparent/glowing materials and the error greeted me:) ac render is unwilling to coorporate with winbox resources, it just crashes.
are you using built-in lightworks render? if so, try altering the sun parameters (ambience/camera/quality/softness). use sky object instead of sun (i never used sun).
