The problem seems to be a null pointer access, likely due to SDL_GetVideoSurface returning NULL. (You should be able to verify that in the debugger, if you find the Locals pane and look at the value of 's'.) It sounds like SDL initialization is failing somewhere. One thing to try: make sure your video card drivers are up to date. Other than that I'm not sure what could be the cause.
You might try adding a line of code like:
printf("SDL error: %s\n", SDL_GetError());
Try copying that in after each SDL call (SDL_Init, SDL_SetVideoMode, etc.) in that section of code. That should hopefully display a more informative error message in the console.