Help, won't POST with more than 1 stick of ram / 790FX-GD70

Hello everyone, I've been pretty desperate for the last few hours.

I recently upgraded my CPU for my PC and ever since, it won't accept more than the classic 1 stick after CMOS clear.
Here's my rig:

Mobo: MSI 790FX-GD70
CPU: AMD Phenom II X6 1100T Black Edtion
RAM: 4 sticks of Kingston HyperX DDR3 KHX1800C8D3K2 (8go)
Power Supply: ZM500-HP - ZALMAN ZM500-HP 500W POWER SUPPLY WITH HEATPIPE
Video: Sapphire Radeon HD 6870

Whenever I add more than 1 stick of RAM, the mobo blinks the FF error.

I've been reading that I need to change some configurations of DRAM and/or CPU settings in the BIOS (which is the latest version 1.H that supports the CPU). I just don't know what to change, I've tried several things and they all still lead to FF and I had to go back to 1 stick.

The PC runs really well with 1 stick for now, I've been playing on it no problems. So it can't be cpu support, it works like a charm. I just really want to get the most out of my rig and I don't want to get rid of 6gig of ram lol.

Any help would be REALLY appreciated, this has been giving me a headache for the past couple of hours, and I don't want to spend time and money in bringing it to a shop. Thanks in advance!

Did you try other good ram ? Maybe the new one you got is not compatible or got fried.
Kanjisan

Did you get this sorted? I'm in the process of upgrading to a GB P67A MB and using the Zalman ZM500-HP which I have been using for about 3 years on an Asus A8N-SLI MB (AMD 64 Athlon) - but the Zalman doesn't seem to cut the mustard - didn't boot - phase LEDs on the P67A-UD3 just flicker and the speaker clicked - changing the PS to another one worked - but I'd like to keep using the Zalman - so trying to figure out what's wrong with it.