Did blizz found a fix for this? for the first time in all my years of playing WOW I got an error problem (BLZBNTAGT00000840). In task manager voice proxy was open 3 times??? Had to end them all to update.
Hey there,
I moved you to your own thread since you bumped a pretty old one. There is a known issue where voice proxy will sometimes get stuck open. If this happens, just end the task like you did and the updates should work fine.
I had to restart my computer for it to be fixed.
Perfect answer Rekttum - thank you so much! 
- went to Task Manager and End Task for the WOW Voice Proxy Service - once it was closed the update worked great.