It just appeared out of the blue, without excessive use, and can't have to do with chassis intrusion jumpers as this mobo doesn't have them. Clearing CMOS didn't help, fan is slow (is it slow?) @320RPM, but CPU is not much more than 54º when rendering. No cables loose.
But everytime I can't load OS. Seems like an issue with this mobo; P8Z68-V, but just within warranty (36mths till November). Frustrating!