UPDATE: As of 11:31 PM EST on 3/28/2011...
While playing AION, my screen froze yet it didn't go black. The environment around me froze and my character became a mass of blue,yellow, green, red, etc lines and squares. The mouse could move around, albeit slowly before the system froze altogether.
 
I believe this would be a sign of my cards dying?
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Alright, to describe my problem specifically, I'll do this in bullet form. Before any asks yes I've checked other threads but I want to try to narrow it down personally before I tinker with BIOs or anything else. I've never flashed bios or manually set timings and voltage without a guide so any help would be appreciated if that is necessary. My temperature are also stable, usually averaging from 42c - 51c when idle depending on my room temperature. I get between 52c - 61c under load (rarely 61c - 68c when playing Crysis on Max) Fan usually runs at between 61% - 80% depending on what I'm doing (idle or gaming) to maintain such temperatures.
 
Important Hardware:

• Evga GTX 285 2 GB (two of these in SLI) Driver Version: 197.45 [Minor note, I do have a sound card between them.]
• Evga 3x sli Motherboard (BIOs version currently unknown, will update with it later)
• 12 GB Corsair XMS3 1600Mhz
• 1000w Corsair PSU
• I -think- I am using a DVI to HDMI cable, with the HDMI plug being in my monitor and the DVI side "screwed" (small handles you twist) into my top GTX 285.

Facts about the Problem:

• Occurs randomly, more frequently when in a game but has been known to occur when simply being idle.
• It occurs a couple times a month if I'm unlucky, though more frequently lately.
• The screen goes completely black though my chosen display option shows in the upper-right corner of monitor as if I just turned it on. Ex. [HDMI] will show for a moment before fading and the power button blinking.
• Sound still plays through my headphones. Music in my games continues as usual, people continue talking over voice chat, and sometimes I can still hear combat sounds. (Note, occasionally the sound will freeze causing a loud buzzing noise or one segment will repeat over and over.)
• Entire computer remains on. This includes fans, LED lights, Hard-drives, and even the keyboard.
• Despite the computer being on, it is unresponsive to any key I press, including combination's such as Alt-F4, Ctrl-Alt-Delete, etc.
• The only way to solve the problem (until it happens again) is a Hard Boot.
• There is no BSOD or error message at all, it simply happens.

OCCT, for any who know what it is, have shown no errors on my cards and Windows Memory Test has shown no errors eithers. I do not have memtest however I have no CD or Flash drive to put it on currently. I am also unable to Overclock my i7 920 higher than the turbo boost (2.67) without crashing despite following guides and using ideal settings which leads me to believe this could be a mainboard issue?
 
Thank you to any who have the time and patience to read this, been trying to solve this problem for two years now and my last resort is to send it in for repairs before the warranty ends this august. Hopefully one of you can shed some light on this issue. -Jag

I'm using the older 197.45 drivers, so I don't have the option to choose which GPU or processor to handle PhysX on. My only option is the following:
 
Set PhysX GPU Acceleration:

• Enable
• Disable

If I choose disable, would that default it to the processor?

My issue seems similar to the OPs.

• My screen goes black.
• I can hear whatever was playing (game or movie) still playing without issue.
• I can change LCD outputs on my G15 keyboard and see that the temps are alright on my system. 
• Issue does not go away with a soft reset, or a hard reset if I do not wait. 
• OCCT shows no faults or errors and temps have remained within tolerances (running under 60c for GPU and under 52c for PBC on both cards). And GPU MEMTest shows no issues..3
• First time it happened my system was idle running overnight (playing music while I slept). 

Now I am use 2x EVGA GTX 260c216 in SLI.
MOBO is the EVGA 750i FTW.
CPU is E8400@3.73Ghz
8GB RAM
Running the 266.58 drivers
 
This problem has only happened a few times thus far. And has been happening for less than a month.
 
I am not trying to post this to take over anyones thread. I am just hoping this helps figure a solution out.

I switched to CPU controlled PhysX and so far no crash, as for the guy talking about the driver I have a problem with mine. I can do the following:

• Delete files Manually
• Use the Device Manager to Uninstall
• Use Driver sweep in and out of safemode
• Use a registry cleaner

I do all of those multiple times and still after I reboot the computer from uninstalling the driver, Microsoft installs a W-something 1.1 driver in it's place, this happens with auto-update off and my connection to the internet (physically unplugged network cable.) So my only option is to install my drivers over it.
 
Bottom Line: The switching PhysX to cpu solution is working, so far. If you use SLI and don't have many background tasks running I recommend trying this.

I suppose PhysX still runs regardless of whether or not an application that uses it is also running or not. Not entirely sure though, I'll post more info from my end if it crashes again, so far it hasn't.

Display went out again, switching PhysX over to the CPU is not the solution for me.

My fan works perfectly, I can hear them both through my headphones. (I always keep them at between 60-80% to maintain 40-50c temperatures) so heat is not the problem as it rarely exceeds 56c under load.
 
I can't RMA because I peeled off the stickers on the cards without thinking and I never registered them. The company that built this PC for me no longer has a website so no hope of contacting them either. :/

I'm personally hoping to drop these two bricks, get a single 580 (or 590 hopefully) and completely reinstall my OS. If that doesn't solve the problem I'm screwed. -_-

I am not using any special codecs. I have not installed anything for this machine specifically. Also, the faulty install of a codec would not explain why it causes a signal loss at desktop on occasion. 
 
So we have me losing video once while using MPC. We also have me losing video while watching a windowed flash video off the CWTV website (Nikita). It has happened while playing Dragon Age Origin. It also has happened while the system was completely idle (I turn on my monitor after waking up and their is no video). 
 
These are somehow related, but so far I do not see the link. I believe the activities are inconsequential to the issue at hand.
 
Now for the idea of installing windows 7 again, I do not relish the thought of reinstalling my over 1.5TB of software (much of which is on Steam and would take me weeks to redownload). I would rather find another option before a clean install of the OS. 
 
 
Edit:
A thought occurs to me that what is new in these drivers are the HD Audio. I wonder if, since I am on a GTX 260 which does not benefit from them, they are causing issues. Just a thought. These issues started after I moved from the 260.99 drivers which did not include the HD Audio. This is all speculation at this point, but worth thinking about. 

I had a problem once where the video signal did indeed drop. It could be one minute, one hour, a couple of days.  I went through hell trying to find that problem. IT WAS INDEED THE MOTHERBOARD that was bad. I didn't want to say that earlier until a lot of testing was done but you seem to have come to that conclusion. 
 
CorpsMaker

Let me know how it works out for you in the long run, if the end of march rolls around and you've not had any more problems, I'll dump these two and invest in a 580 (or maybe wait until the 590?)
 
On the upside, it could be the cards. I switched their places recently and found this blue flickering all over my screen. Hopefully replacing them will solve this problem for good. But a quick question... Have any of you when uninstalling drivers and restarting, been met with Windows 7 (or Vista) telling you a "Microsoft WDDM v1.1" driver has been installed for your cards? It does this whenever I attempt to update my drivers even after previously removing everything via manual uninstall and following up with Driver Sweeper in safe mode.

My GTX 285 2 GB cards do not like anything after the 260.99 drivers either, similar issues.  While playing COD Black Ops the video driver crashes, screen goes black and sometimes it come back to the game, but FPS are horrible after the recovery and the system needs to be rebooted to resolve it.

me have'ing same problem but later i figure,d it out its my dvi cable who went bad so changed it now no more black screen after exiting game !

Update for me, just tonight as of 11:31 PM EST on 3/28/2011...
While playing AION, my screen froze yet it didn't go black. The enviroment around me froze and my character became a mass of blue,yellow, green, red, etc pixelation. The mouse could move around, albeit slowly before the system froze altogether.
 
I believe this would be a sign of my cards dying?

Still looking for help in regards to my last issue. Are these things dying or what?