RAM Passes Memtest But Causes Freezing?

[mm66554]

RAM: OZC Gold 1600
MoBo: Asus Rampage II Extreme

Really frustrated with this... Been trying to sort this problem out for months, I just got done testing my RAM in memtest... each stick individually in a separate slot... all over 10 passes at these settings:

1600MHz
8-8-8-24
1.65v

Yet when I test them all at once Memtest freezes at 4 seconds

Whats more, each stick causes my comp to freeze, even when only one is inserted, apart from ONE stick, at these settings (stock):

1066MHz
7-7-7-20
Autov

So this is confusing me... why does this one chip work at faster latency but not slower? Why do each of the chips pass individually but not all together?

Is there any other tests I can do? How can I tell it's the MoBo not the RAM?

Thanks.

*edit*
I should mention that this one chip passes memtest at 7-7-7-20, whereas the other 2 don't. All pass at 8-8-8-24 though.

Memtest version 3.5 (4).

 

[Slaymate]

Those Modules are rated for 1600MHz @ 1.7volts. Make sure your CPU VTT voltage (also called DRAM/QPI Voltage) is at 1.2v or higher, it must stay within .5 volts of the DRAM Voltage.

OCZ DDR3 PC3-12800 Gold Triple Channel OCZ Technology