You will have to be methodical with memtest. First this version (5.0) is for SB-E.... it is a Beta but works perfectly.
http://forum.canardpc.com/threads/68001-Memtest86-5.00-Beta-available-%21-Need-betatesters-%21You will have to run all tests at auto or at XMP......don't change until you have run all possible combinations.
You will have to eliminate bad sticks or bad slots. So run one stick in one slot. If errors run a different stick in the same slot. If this happens 4 times then the slot is bad or all sticks are bad. So try a different slot.
If the first stick passes in the first slot move that stick to another slot to test the slots for errors. If a slot gives errors try another stick in it.
If a random combination of slots and sticks sometimes give errors sometimes not then it will be something else.
When you test multiple sticks together follow the manual for placement.
Another thing you could do if one stick passes on one slot stop RAM testing and test your CPU with IPDT
But yes! You are on the right track;) just have to experiment to find out what's going on.
Is your PSU new....what model....can it be trusted?