I just did a fresh format and re installation of Windows 10. Then I downloaded and installed the latest version of Prepar3D from the LM website, not aware of the SLI issues being reported. I have two 780's in SLI, and the first time I launched the simulator it was absolutely unplayable. The next time I launched the game, it hung on the loading screen at 100%. After disabling SLI, the sim performed as you would expect from a single gtx 780.
I certainly hope this issue gets fixed soon, since I didn't backup my previous version of P3D before restoring my computer.