SLI crash

[youpla]

I recently got random crashes on my system while playing games or watching flash embedded video: black screen, buzzer noise until PC reboot.
I previously reported that I sometime get an overheating PCIE-2 warning (over 60C) http://forum.overclock3d.net/showthread.php?t=67250
I decided to turn off SLI and it seems the crashes disappear!
How can I check if it is the PCIE-2 slot that is malfunctioning or if it is the GFX card?
My rig is described in my sig and I am running the latest 344.11 nvidia drivers...
TIA

 

[SPS]

Use the graphics card from the other slot and see if the issue persists.

 

[youpla]

Well I noticed that my second card led (next to the PCI-E power connectors) were off.
I unplug both card and switch the power cable of the video card1 to the video card 2 and vice versa and then both cards got there power led on!
And it seems it's not crashing anymore, so I guess it's because my second card lost power occasionally because of bad connection!
It's strange though because I never touched the power cable and everything was working great.
Is it possible that somehow my PSU is dying on me?

 

[YouWhat]

Well I noticed that my second card led (next to the PCI-E power connectors) were off.
I unplug both card and switch the power cable of the video card1 to the video card 2 and vice versa and then both cards got there power led on!
And it seems it's not crashing anymore, so I guess it's because my second card lost power occasionally because of bad connection!
It's strange though because I never touched the power cable and everything was working great.
Is it possible that somehow my PSU is dying on me?

Yes it is possible that it is dying, but it is more likely that the vibrations from the fans running on the card have loosened the cable plug slightly which is why when you re-seated it, it worked flawlessly again.

Just keep an eye on it for new few days, stress test it also when you get chance as this will more thank likely show up any problems.

 

[youpla]

I guess that may also explain why I got this pcie-2 temp warning, maybe the card tried to draw all the power from the pci slot when the connection with the power cables loosen up!
anyway I'll surely look carefully at any other signs during the next few days...
I ran unigine at max settings and it went fine!