Some more system information would be helpful. Are you using 2 GPUs? What GPUs? Does Nvidia control panel show your monitor set up?
 
This is how mine is set up, although Im using SLI and a dedicated Physx card too.
 
EDIT: Note placement of connections, Monitor 1 is the Sceptre, Monitor 2 is on the dedicated Physx. The cables are connected as pictured in the Nvidia control panel. If your using 1 GPU, Monitor 1 should be where my Sceptre is and obviously monitor 2 in the second connection. 

 
Also what are your display settings in windows??
 
Should look similar to this:
 

try control panel diplay tab.

I had a lot of crashes with my expereince with SLI, I started with Vista and had 2 8800 GTS 640s by XFX and this model 750i FTW, I wanted to play Crysis (1) and Far Cry 2 so bad but it would BSOD after 20 minutes of playing either of those intense games and I could only play those games with SLI enabled so I was obsessed at the time. I RMAed the motherboard once after weeks of troubleshooting and still no dice at that time Win7 was comming out so all of that work was essentialy a waste because Win7 was probably built better to handle those problems and I ended up being nice and selling my 2 XFX 8800 GTSs for inexpensive and trying the 295 which wasn't a whole lot better and was really expensive for the heat that generated it was the dual PCB version the orgional. Now with nVidia's major leap in graphics to Fermi architechture I have 1 EVGA 480 and can game at least cross my fingers hopefully for a while, I probably didn't need to RMA EVGA's board if I would have stuck to my guns a little more with the notion that Vista was essentialy the Windows BETA of future operating systems.
 
My system's cool but I do cross my fingers that I don't snap something when I am moving something around with the side panel open and it is just cooled on air right now. I am rediculiously satisfied with how stable it is relatively.