Not saying these will work, but NVIDIA has new Beta drivers
they release on July 11th. Give them a try and see if SLI is working. Use Driver Clean Pro to remove the old NVIDIA drivers. I dont have SLI but these drivers work great. I havent had a single problem playing Lost Planet.
This driver supports single GPU and NVIDIA SLI™ technology on DirectX 9, DirectX 10, and OpenGL.
Improved compatibility for Lost Planet.
Added "Resize the HDTV desktop" underscan compensation option
Numerous game and application compatibility fixes. Please read the release notes for more information on product support, feature limitations, driver fixes and known compatibility issues.