Will Horizons support SLI? It seems pretty stable in normal mode but in SLI, it's like being inside a surreal painting with clipping everywhere and strange lines/slabs of solid colour all over the sky - but worst of all, what you're looking at directly, simply disappears... I have a pair of old 550's in SLI mode. (but, I have to sat, the game just about runs acceptably in normal mode too...
Same here even after manually identifying the exe in nvidia control panel as micheal suggested, as soon as I get close to the planet it's like flying into a dustbin full of chess boards.