did it sound like this http://www.youtube.com/watch?v=ne9IjmM4DXw&feature=plcp
happened to me in headstart, hasnt happened since. Pretty sure this has to be some quirk in the sound engine for GW2 as this has never happened in any other game.
Although as Nitrius said, this could also be some sort of driver conflict.
(X-Fi Xtreme Gamer sound card)
Oh God, oh God we’re all gonna die?