Did you get the RAM stable?
What is the RAM frequency?
AMD CPUs have issues with RAM frequencies above 1333MHz, you need to increase the NB frequency to 2000-2400MHz to get it above 1333MHZ.
What is the DRAM voltage?
With more than 4GB RAM you will need to bump the CPU NB (IMC) voltage, bump it to 1.250v and test with memtest86+, this is a common issue with AMD systems.
If still not stable bump again by 0.02v until stable, if you get to 1.35 to 1.40v then you will need to look at DRAM voltage or other causes..
If stable then lower it by0.02v until unstable and bump it back up 0.02v, should be good.
Just like when you OC RAM, adjust and test.
This is the abbreviated version, let us know if you have any questions.