FYI, I'm having the same problem and I'm running the game on my laptop under WindowsXP. This isn't a Vista issue. No other complaints with the game so far. I've seen the spinning NPC happen elsewhere when I run around an NPC quickly (eg. with shopkeepers that always turn to face you). Once the NPC starts spinning, the game usually crashes. The problem with the occurence in the church is that it happens during the cutscene, so you can't just reload and work around it.
