Visual C++ Runtime Error most likely means that the Launcher application crashed (it is quite unstable for me, more so than the game itself), though that's never caused any problems for me. What does it do (or doesn't do) when you try to launch it?
First thing to try would be to use Steam's "Verify Integrity of Game Cache" (in library, right click on game title, select properties and go to the "Local Files" tab.) You'll need to redo all changes to Fallout_default.ini after this.