Rig details in signature.  I just upgraded the PSU and an additional GPU, and then the issues started manifesting.  Old PSU was an OCZ 700W.  Issue details:

On Battlefield: Bad Company 2 after approximately 20 minutes of game time, I'll get an audio and video stuttering that, after 5 seconds, will cause the video feed to disappear, and either the audio will continue to keep playing/loop, or the entire system will be locked up with no video feed.  I have to do a cold reboot, after which everything works fine.  Other programs, such as Crysis 2, I do NOT have any issues.
 
Event log did at one time show that the Desktop Windows Manager was causing an issue, but disabling it yields no results.  Just recently after a crash, a BSOD error comes up showing the following:
 
BCCode:    116
  BCP1:    FFFFFA8006FE54E0
  BCP2:    FFFFF88010634FA4
  BCP3:    FFFFFFFFC000009A
  BCP4:    0000000000000004
 
Apparently, error 116 has to do with the the video card response timeout.  All my leads in that direction never panned out.
 
Event log shows no other information at the exact time.  I am running GPU-Z on both cards, SpeedFan, CPU-Z, and EVGA Precision to monitor temperatures.  All temperatures are in satisfactory limits (top GPU @ 69C, bottom GPU @ 59C, CPU @ 70C).
 
Since then, here's what I've done:
- Rolled back drivers (current drivers were up to date), then re-installed recent drivers after DriveSweeper
- Disabling SLI in nVidia control panel
- Changing positions of cards in PCI-E ports
- Using only one card at a time (both old and new still crashed)
- Resetting/updating BIOS
- Deleting anti-virus
- Format and re-install newest drivers for ALL devices
 
Since the fresh install, I've kind of hit a brick wall.  I've Googled this issue way more times than I can count.  My day job involves troubleshooting issues, and I come home to this and end up staying up late trying to fix it.  I'm kind of out of energy.  Every forum I've seen has recommended issues that aren't the problem.  The fact remains, I didn't have this issue until I installed the new PSU and GPU.  So you would think it would be one of the two, right?  Well, I decided to install my old PSU and use my original GTX 460, go back to my original rig.  Problem happened again.  Even using the old PSU and the new GPU.   
 
Since I've taken care of every single software issue I know of, I tend to think it would be hardware.  I thought of two possibilities:
 
1. The motherboard is bad.  Unfortunately, I don't have the cash to purchase a new one, and no one I know has a spare.
2. The old 460 was fine, but suddenly, with the new PSU, began manifesting issues.  Also, the new 460 shipped from the warehouse with the same exact issue (remember, I tried both card independently and got the same problem).
 
Can anyone help me?  I'm really frustrated.  I went out and spent a lot of money on upgrades and it's been nothing but headaches.  I spent my entire day off trying to fix this and I'm just worn out.  I can't even go back to the way things were.  I really need some informative help, not random people talking about stuff that they're not completely knowledgeable on.  Anyone else dealt with these issues?  Should I just RMA one card at a time and see if those are the issues?  Thanks for reading.

I agree, half your problem is running those 4 monitor programs together.
Specifically, speedfan is inaccurate, mostly in the voltages, and it conflicts with the others. As was recommended in above post, remove them all, but precision (2.03 seems a bit more stable). To monitor cpu temps, use core temp, or real temp.
Also download CCleaner, (free at CCleaner.com), install, clean system, then registry. Restart.
Then, clean install 267.24 (beta at nvidia.com or geforce.com)....
Also disable the HD audio controller for cards.
BTW- do what I suggested in the order listed, (download what you need to before beginning).
As an aside, the HX's seem to have more problems/failures than the excellent Gaming or Pro Gold series. An excellent resource when looking for a new psu is JohnnyGuru.com They do intensive reviews/testing of all psu's, which you can use as a very reliable guide....(If you're within the 30 day window, return the HX and get a gaming GS or pro gold AX)... 
It would probably be best to download all needed drivers and programs, save to your storage drive in a new folder. Reformat OS drive, fresh install windows, add suggested programs/drivers, then install your games. But, if you follow my ramblings, it'll work too. 

Maniac, I don't know how to say it...but you've got voodoo in you.  I deleted all nVidia through control panel, restarted, loaded the 267.24 drivers, set everything in the NCP to your settings (except for the Anisotropic Filtering), and, at the hefty cost of no sleep, I ran the game for the past hour with no issues. I've not tested any other games, but those weren't the issue, just BF:BC2.  And DAMN, the graphics looked better than they ever have. 
 
Usually my top GPU would max out temperature wise at 65C, I had it running up to 74 and my bottom at 56.  One core topped 86, but I'm getting a Venemous X in the mail so I'm not worried about that. 
 
Man, you just plain ROCK.  I've almost been pulling my hair out.  This is the long end for a very difficult journey, I hope others can find this and learn.   If you're ever in NYC, hit me up.  I owe you!
 
The only thing that still bugs me is why this only became an issue after the second GPU was installed?  Many thanks.  Big ups to Polk as well, I really appreciate it.

maniacvvv

hawkens85

Maniac, I don't know how to say it...but you've got voodoo in you.  I deleted all nVidia through control panel, restarted, loaded the 267.24 drivers, set everything in the NCP to your settings (except for the Anisotropic Filtering), and, at the hefty cost of no sleep, I ran the game for the past hour with no issues. I've not tested any other games, but those weren't the issue, just BF:BC2.  And DAMN, the graphics looked better than they ever have. 

Usually my top GPU would max out temperature wise at 65C, I had it running up to 74 and my bottom at 56.  One core topped 86, but I'm getting a Venemous X in the mail so I'm not worried about that. 

Man, you just plain ROCK.  I've almost been pulling my hair out.  This is the long end for a very difficult journey, I hope others can find this and learn.   If you're ever in NYC, hit me up.  I owe you!

The only thing that still bugs me is why this only became an issue after the second GPU was installed?  Many thanks.  Big ups to Polk as well, I really appreciate it.

Thanks Bro, great job and happy gaming

Great job, man.......gratz on your BR assistance!!