Oh yea all drivers work fine in single but I have to apply the patch since my mobo dosent support SLI (physically it does and thats what the patch is for), if i dont apply the patch all i can use the secondary card for is PhysX. I use the 1.42b from www.slipatch.com
and the release v1.0 from russian xdevs.
My previous problem was that any drivers higher than 266.58 would screw up SLI on either patch v1(xdevs) or slipatch.com's 1.42b, whenever it was enabled in the nvctrl panel both cards would stay at idle 2D speeds of 51MHz and AB would be locked down exactly the same way this fellow had with his 560ti (scroll down a bit till you find the picture)
Apparently the cause is that when the patch is updated it leaves some leftover routines that screw the latest drivers and patch (not that 27x was that great anyway), to fix it you had to either swap or take out both cards which forced windows to re-do a hardware install removing the drivers and the patch with all its leftovers. Re-applying the latest patch and drivers supposedly fixed the problem although i've been a bit busy lately so I havent got around to testing it personally.