Update: The worst has happened. I've always been able to do the non-5.1 content until tonight. I tried teleporting to Rak'tika woods and I crashed (no error, no popup) before even ending the teleport. Now my character is in that zone, but I instant-crash before the loading screen finishes when logging back in. The loading screen appears to be in an endless loop (the image with a spinning loading wheel).

I AM NO LONGER ABLE TO LOG ON AND PLAY BECAUSE OF THIS.