1-2 (the 2 closest to the CPU? If so, it may be a channel problem, might try loosening the CPU cooler then snugging it back down, if the cooler is too tight in a corner or side it can throw the MC (memory controller) out of whack from all pins not getting full contact - another item to pull the CPU and check for bent/broken pins, debris in the socket or excess thermal compound in socket or on bottom of CPU