I remember a few years ago I was at a concert and afterwards I had to hit the men's room.  I was standing at the good old urinal when someone a few slots away from me sneezed.  

That created an internal conundrum.  I've been conditioned for several decades to say "Bless you" when someone sneezes, but I've also been conditioned for several decades not to talk to other dudes at the urinal.  It was like I had a mental computing error and my brain locked up.  I don't think I ended up saying anything, but it wasn't because urinal etiquette won out.  It was more that I just froze up and couldn't do anything.  If I had been a computer I would have definitely crashed.