After the obligatory updating every driver and reinstalling the game twice pain in the ass, and trying the old FO3 fix for this same issue (put d3d9.dll in the game directory, remove the intro movie file and edit out three line in the .ini file(s)), not to mention screwing around with my graphics settings and compatibility mode for FalloutNV.exe, it turned out to be an ffdshow issue. I had to add it to the exclusions list for both the video and audio configurations, and after about 4 hours of screwing around with other @#&$ that didn't help, it took 30 seconds in the ffdshow configuration GUIs to get this game running.

Putting this up there in the hopes it might help someone else get the game running, or make it into an official list of stuff to try before flaming the tech support forum, or w/e.

Had exact the same problem, messing with FFDshow had no use, fixed only after reinstalling Windows...
GL