On all of the stickers it says "1333MHZ" so im unsure why two of them are 1600mhz to be honest
Did you also try the other two sticks and get the same results.
When you tried the Ram in slots 1 and 2 did you check to see what speed it was running at, if not please do so and then do the same with the other two sticks.
From my reply #12;
No OCing is good but to see if it helps any try restoring the MBs most stable/default factory settings in the BIOS.
Have you tried restoring the MBs default factory settings - please note that optimised settings should not be selected as it is a form of overclocking and can make a computer unstable.
I also looked at task manager while playing the game and surely the game shouldn't be using this much RAM? http://gyazo.com/e0b...11220f4d752bd9f
My RAM usage was on about 98% when I was playing with just the 2 sticks of RAM inside.
A GTA V thread here regarding Ram usage, stuttering and freezing etc