I'm reminded of the Troicki-Ferrero match this year down under, during which Viktor had a fan chucked out for shouting: "Hey Troicki, how do you say choke in Serbian?" A lot of people claimed that guy was a racist, but I'm not sure if Viktor gave any reason for complaining other than that the guy was being annoying. The incident's on Youtube:
http://www.youtube.com/watch?v=EDJOgQ19dJU