I have been having freezing issues with my 790i Ultra SLI for years. The freeze locks up my mouse, keyboard and anything on the screen and the only option is to hard shutdown or reset. When I get the problem I am usually on Google Chrome watching a YouTube video, video chatting in either Gmail or Skype, playing a Facebook flash game or many other websites. I have had it crash the second after the Gmail chat notification sound (which requires flash to be running). It will crash in some games but I can play Skyrim or BF3 for hours without it doing anything.
Lately after combing these forums I have set my Mobo to settings similar to what others have recommended with the same problem.

I have noticed a trend in the frequency of the crashes when ONLY adjusting the Voltage on my RAM. The recommended voltage on my dimms are 1.600V and I have tried every .250V increase up to 1.900V seeing a decrease in freezes as I increase the voltage. Around 1.800V is where the freezing occurs less, and 1.600V is where the freezing occurs much more frequent.

I have tested my system without my sound card and it still crashed at 1.600V without any sound card or sound altogether.

I have tested my RAM with memtest86+ (on both dimms which have passed using 1.800V), Intel burn test at Max strength, and with OCCT for one hour. All tests come out reporting zero errors and they run fine.

Here are my system settings (which are in my signature as well):

QX9650 3.00 GHz 1333FSB 12MB L2 Cache 64 Bit
EVGA nForce 790i Ultra SLI
Corsair XMS3 4GB (2x2GB, Black slots) PC1333 DDR3 PC3 10666 Dual Channel Memory (TW3X4G1333C9DHX)
Timings (recommended): 9-9-9-24 at 1.6 volts
EVGA NVIDIA GTX 280 1GB PCI-E
C-Media CMI 8768+ PCI Sound Card
Intel Pro Gigabite 10/100/1000 Network Card
WINDOWS 7 64bit ULTIMATE  
NZXT 800 WATT POWER SUPPLY SLI

Here are my BIOS settings:



BIOS Version: P08
**System **
CPU Freq, MHz: (3000.0)
FSB Reference Clock, MHz: (1333.3)
CPU Multiplier: [9x]
CPU N/2 Ratio: [Disabled]
PCle x16-1 & 16-2, MHz: [AUTO] (100)
PCle x16-3, MHz: [AUTO] (100)
SPPc->MCP Ref Clock, MHz: [AUTO] (200)
nForce SPP --> nForce MCP: [5X]
nForce SPP c-- nForce MCP: [5X]
**Spread Spectrum**
CPU Spread Spectrum: [Disabled]
HT Spread Spectrum: [Disabled]
PCle Spread Spectrurn(SPP): [Disabled]
PCle Spread Spectrurn(MCP): [Disabled]
SATA Spread Spectrum: [Disabled]
**FSB & Memorv Config**
FSB - Memory Clock Mode: [Unlinked]
FSB - Memory Ratio: FSB (QDR), MHz: [1333.3]
Actual FSB (QDR), MHz: (1333.3)
x MEM (DDR), MHz: Linked (1333.3]
Actual MEM (DDR), MHz: (1333.3)
P1: [Auto]   
P2: [Auto]
**Memory Timing Setting**
Memory Timing Setting: [Expert]
tCL (CAS Latency): (9)
tRCD: (9)
tRP: (9)
tRAS: (24)
Command Per Clock: [2T]
** Advanced Memory Settings **
tRRD: [Auto (5)] (5)
tRC: [Auto (34)] (34)
tWR: [Auto (12)] (12)
tWTR: [Auto (16)] (16)
tFAW: [Auto (21)] (21)
tREF: [Auto] (7.7us)
tRFC: [Auto (74)] (74)
**System Voltages**
(Manually set the System Voltages)
CPU Core: [Auto] (1.17v)
CPU FSB: [Auto] (1.10v)
Memory: [1.800v] (1.800v)
nForce SPP: [1.40v] (1.40v)
nForce MCP: [Auto] (1.500v)  
(Leave on auto)
GTLVREF Lane 0: [AUTO] (-30mv)
GTLVREF Lane 1: [AUTO] (-30mv)
GTLVREF Lane 2: [AUTO] (+00mv)
GTLVREF Lane 3: [AUTO] (+00mv)
**CPU Configuration**
Limit CPUlD Maxval: [Disabled]
Intel Speedstep: [Disabled]
xPPM Mode: [Native MODE]
CPU Thermal Control: [Disabled]
C1E Enhanced Halt State: [Disabled]
Execute Disable Bit - [Enabled]
Virtualization Technology: [Disabled]  
CPU Core 0: [Enabled]
CPU Core 1: [Enabled]
CPU Core 2: [Enabled]
CPU Core 3: [Enabled]
 

RAM is in black slots (has been) and I made the adjustments. 
 
It did freeze again last night but seemed to take a lot longer than normal using 1.600V for my RAM. 

Yes it is stated on the RAM itself that the timings are 9-9-9-24 at 1.6 volts.

No Blue Screen. The mouse and keyboard become unresponsive, any websites loading or games being played lock up and the last display is the only thing that shows up on my monitor. The display does not turn black or anything. Any audio repeats the last half second over and over in very quick repeated fashion. The only way to get out of it is to hard shutdown or reset on the buttons on my tower.

I am using version 290.53. Do you think it could be this video card? I have not replaced or upgraded it since I got it in 2008 and it has been doing this "freeze" since the same time.

I tried using an old video card (ATI x850xt) and the computer still froze in the exact same manner. I was watching a YouTube video at the time and decided to record what it looks like when it freezes: http://www.youtube.com/watch?v=c8TjW53Rue8. Would you still say it is a video card issue?

I started running Memtest and it got stuck at 25:00 minutes as well as 1:00 minute into the test. The time did not increase and it seemed that it froze on the test. I put one RAM DIMM in the furthest left (closest to CPU) slot. I have posted about this issue back in 2009 here: http://forums.evga.comarchive/printable.asp?m=100913366. It froze last time I tested the  RAM when the voltage was at 1.600V and was told to increase the voltage and try again. What does that say about my RAM if it cannot pass Memtest at the manufacturer’s voltage settings? What do you suggest I do?

Thanks for all your help, I am going to try to RMA it. If it does not work out should I try some of the RAM suggested in some of the other "upgrade my RAM" threads?