It's been an issue since I first bought my G.Skill sniper 1866 sticks. I actually RMA'ed 2 sets of snipers because of it not being stable. By the 3rd set I started to realize that it may not be the sticks but the Imc. Now that I own numerous sets of ram and have tried all of them on the 8350 without luck my best guess is the Imc just doesn't like running above 1600. I've hit it with more Dram V, Cpu Nb v, loosened the timings etc. Still every few days if I'm running at 1866 it will randomly lock up and have to be powered down and restarted. Doesn't matter if the Pc is under load or just sitting idle. My 6300 on the other hand is running at 1866 with the snipers installed as I'm typing without a hitch.