Could be anything
Either a bad riser, either your overclocked too much, undervolted too much, your PSU is crap, or it just crashed due to bad luck.
Just set the watchdog on and just let claymore reboot the software and it should work again.
What overcloak and undervolt settings do you recommend?
Also, How to do so: "Just set the watchdog on and just let claymore reboot the software and it should work again." ?
Thanks.