Having 3 GPU in SLI, since last night I found out that running 3Dmark11 would get really low score.
I ran a few test and found out than 2 out of the 3 cards were kicking out of SLI in 3D mode by the driver and I could not re-enable SLI using the driver unless I reboot the computer. The phenomenon was quite strange because GPU-Z and the nVidia driver would tell me SLI was enabled but when I ran anything in 3D, only one card was being loaded. Also every time I would reboot, SLI would be enabled during the benchmark up to a certain point where it would suddenly kick out and the fps would drop like a rock. This was very repeatable.
After tweaking voltages and all kinds of other parameters, I remembered that I plugged a USB 2.0 hub into the USB 3.0 port yesterday to connect a steering wheel.
Once I unplugged it and rebooted the computer, everything is now back to normal.

Thought I would report it. The X58A-OC uses an Etron USB controller. I am not quite sure what happened there and it is one of the strangest problems I have encountered. The USB management of this board has seemed a little flaky. I am also using an USB sound card which... makes my mouse and keyboard stutter until unplug it and plug it back after windows is loaded...