I think what I did to get both working was 3 things, not sure exactly which one did it.
 
Set it to gen2 I also have an i7-3930k
Flashed BIOS to newest and Reset bios by unplugging PSU and removing battery.
I also loosened the set screws on the AIO water block a turn each. I think they were too tight and my gut tell me that was the fix. Too much pressure on the CPU.
Did those things one at a time and tried it, no go, did the screws last still no go.
Got mad and turned it off unplugged it and walked away. Went to bed and slept on it.
Turned it on next day and it was working. Each and every time I tried it worked. Still working today.
Sorry I could not be more specific. Hope you get it fixed.

bill1024
...I also loosened the set screws on the AIO water block a turn each. I think they were too tight and my gut tell me that was the fix. Too much pressure on the CPU.

lolwut.

bcavnaugh
Back to cannot edit Posts the File is force-enable-gen3.exe from
http://nvidia.custhelp.com/app/answers/detail/a_id/3135/~/geforce-gen3-support-on-x79-platform

Thanks for that; I tried it, didn't work, but do I appreciate anything and everything.
 
I shut off the system last night, booted this morning, got SLI.
 
Maybe...just maybe...hot-booting the system is the problem.  Maybe a cold-boot is the key.  This crazy theory I will try, for justice.

karymcfadden

bill1024
...I also loosened the set screws on the AIO water block a turn each. I think they were too tight and my gut tell me that was the fix. Too much pressure on the CPU.

lolwut.

When you bolt down the CPU cooler , it is possible to over tighten the screws, nuts, bolts what ever you want to call them. Four of them, one on each corner.
You are not supposed to crank them down all the way, just tight enough to keep the CPU in place.
If you put too much pressure on the socket it can flatten those little contacts in there and loose connections, if not tightened evenly you can even crack the silicon in the CPU.
I have seen several people say they have fixed all kinds of problems by loosening the set screws. couple times memory issues, but the CPU must have some contact to the GPU through those connections.