Crash and errors with F3-12800CL9D-4GBNQ

[Ocelot07]

Last week I tried to use this memory on this system:

ASROCK AM3 890GX Extreme3 AM3 (GBL/R/V/F/DDRIII)
ASUS Radeon EAH5850 DIRECTCU/2DIS/1GD5 1024MB
WESTERN DIGITAL CAVIAR BLACK 640GB WD6401AALS
CORSAIR TX650W
AMD PHENOM II X6 1055T Soket AM3 2,8GHz - 9MB Cache - 125W Box
G.Skill DDR3 1600Mhz 2GB Cl.9 F3-12800CL9D-4GBNQ (2x2gb)
Microsoft Windows 7 Home Premium 64bit IT

I immediately had some problems with the configuration: in fact suddenly the system rebooted (in idle also) and memtest 86+ found a lot of problems.
Now, after I tried some different memory configurations on BIOS settings, memtest 86+ don't find any problems but the test memory of Windows 7 find hardware problems.
Do I have to do RMA procedure or is there a solution in the configuration?
In case, how long will I have to wait for replacements in Modena, Italy?

Excuse me for my English but I'm Italian.

[mrcmtl]

Did you leave everything at AUTO in the bios or did you tweak it a bit?

[Ocelot07]

The settings now are:
-DDR3 1600 800Mhz
-Voltage at 1,447V
The other are the default settings; now the system seems stable, and an other memory test of Windows 7 didn't find any problem, but I'm going to do an other test with memtest.
If it will give positive results, can I be sure that in future the memories won't give problems?

[mrcmtl]

When you mean voltage at 1.447, what voltage are you referring to?

And yes, if memtest passes a couple of runs, you should be good for a while.

[Ocelot07]

I had a mistake...I wanted to said 1.547V for DRAM Voltage...
And I had no errors with memtest for 2 hours.
Why at the same voltage and settings (I only inverted the position of the two DIMMS), did memtest give different results ?

[mrcmtl]

Often, motherboards memory slots aren't made equal. I have no idea why but there are some slots stronger than others.

[Ocelot07]

Ok thank you for the answers.