ok this is weird because the same exact thing happened to me today.
I tried out those new 236.14 drivers yesterday and had some weird things happen to I did a driver sweep and went back to 260.99 but today I went to play BFBC2 vietnam and I hung up on a loading screen like 3 times causing me to have to hit the restart button.
After restarting that last time only 1 gpu was recognized, I was like oh no, maybe a video card died. So I swapped them and put the bottom one in the top slot. The bottom one wasn't even warm and the the top one was, like oh man dead, so anyway it worked in the top spot???? ***??? So I cleared the cmos and booted up stock (1st thing to try) and same thing.
So thinking that my mobo may be shot, I decide to take it apart, re-seat my cpu cooler and build it on the desk. I do that and everything seems to work fine??? but then I enable SLI (which I never disabled so that was weird) and my image quality is terrible on text, could tell immediately. So I reinstall the driver and enablle/disable/enable SLI and bam back to good.
I rebuilt my pc back into my case, re-did my OC and have played all my games and done a few benchmarks with no problem.
Not sure wth happened but I did get some weird action after installing that 263.14 driver.
OKAY, I was watching video's on youtube and all of a sudden my computer froze up.....
I hit the restart on my machine. Once I logged in, the welcome screen went all pixelated and all different colors, the computer restarted and did that like twice...
Next I decided to play black ops, the game looks all weird, it has a red hue to the game.... what do you think is going on?
Is one of the cards dieing?
I have had this system for only a few months and one of the cards is already on its way out?
after you saying that, make sure your SLI bridge is on all they way. If it is, do a clean reinstall of your drivers.