I'm wondering what that error code means, other than that the game failed to start. This is (fortunately) an intermittent problem, but it either started when I bought Lonesome Road or is another symptom of the Steam update that seems to be a common theme here. BTW, I followed the steps in the sticky to validate the cache, and each time one file fails, one time two. After each of those I have started the game from the regular launcher and not via FOMM/NVSE in order to allow the game to reload those files without worrying about mods. I also tried deleting the ini files with no apparent effect. DXDIAG on request. Thanks!

[Edit] I also notice that when it's about to fail, it spends a couple of minutes displaying "updating Steam" even though presumably it just updated Steam the last time I launched the game.