I’m getting this error (BLZ51900062) all the time. I was just playing and it booted me out with it. I load the game, choose my character, but then it throws the error again when I try to enter the game.
I have of course not changed my account information, I’ve been playing the game!
Found this on Google, I actually encountered this at around 23:00 (GMT) so around the time you posted. I only had it the once, but it made me worry that my account had been accessed from elsewhere.
Seeing as it happened exactly the same time, I’m wondering whether the servers were glitching out? I turned in a quest and then this error popped up.
Fingers crossed someone has some information for us!
EDIT: Just noticed you’re actually on the same realm as me too - could be something to do with it!