Since I built my system about 4 weeks ago I'v been getting random freezes, Sometimes it can happen directly after startup and sometimes it wont freeze up for 3-4 days of 24/7 running. It seems to be happening under all stress loads but mainly when the CPU is under 10% load. It doesn't give me a BSOD or anything, it simply just freezes and repeats the last sound before the freeze until I shut it down by the power button.

I'v re-seated everything in the system except the CPU, Cleaned the RAM sockets and gold fittings.

None of the components have been clocked above their factory settings as of yet, don't want to overclock them until I sort out these freezes.

Temps are all well under the rated max temps, the highest the temps have been are below
CPU: Low load: 16-21°C Full Load (100%) 40-43°C *(From HWMonitor by CPUID)

GPU 1: Low Load: 25-30°C Full Load (100%): 45-50°C

GPU 2: Low Load: 23-27°C Full Load (100%): 45-50°C *(GPU Temps from Catalyst Control Center)

General Case temps Rear: 18-20°C Mid: 20-21°C Front (HDD/SSD Bays): 14-19°C

(Case temps may be a little off as it's from the Kaze master pro fan controller)

I have Un-installed EVERY driver for Motherboard, GPU & Soundcard and Re-installed twice.

Windows is all up to date.

To date i'v tried the following
Running Memtest for 24 hrs straight, No errors
Running Memtest on each individual RAM modules, No errors
Reseated everything except the CPU
Cleaned DIMM Sockets and Gold inputs
Tested the Graphics cards 1 at a time
Re-arranged all the SATA devices to run on Chipset controlled ports
Re-installing all drivers

OS: Win7 Professional 64bit
Motherboard: ASRock X79 Extreme9
CPU: i7 3930k 3.2GHz
GPU: Sapphire 7950 OC Edition V2 (2 card Crossfire)
RAM: G.Skill Ripjaws Z F3-17000CL11Q-16GBZL 16GB (4x4GB) DDR3
Boot Drive: OCZ Agility 4 128GB
Data Drive 1: Western Digital Black 2TB
Data Drive 2: Western Digital Black 2TB
Data Drive 3: Western Digital Green 3TB
Power Supply: Corsair AX1200 Gold