I have the same Tyan board as you. I can happily report that after my initial problems with enabling SLI, everything is working perfectly now.
For my dual GTX 590 setup, I first had to get the latest Tyan BIOS to even be able to boot into Windows properly. After flashing BIOS, I installed driver 267.91, SLI patch version 1.2 beta and rebooted PC. Quad SLI was now selectable from the Nvidia Control Panel. I also installed EVGA SLI patch version 38, but I have no idea what it actually does.
I have to say Metro 2033 looks stunning on my system with highest settings and PhysX enabled. So thanks to anatolymik & co. for the ongoing support
BTW, it seems that a lot of the problems (most?) reported here are not directly related to SLI patch itself, but driver or system problems.