I have this same problem, I don’t do much WvWvW (at the moment), but it has happened 3 times, twice killing the Claw of Jormag (the second time it actually crashed my computer) and once just now fighting the Risen Priest of Balthazar in the Straits of Devastation.
I have an Intel I7-3770K 3.5GHz, 16 GB of Ram and a Sound Blaster X-Fi Fatality card. running Windows 7 Ultimate 64.
I will try the trick with lowing the audio quality and see if that helps.