Not sure my issue is entirely related to this but pretty much since I got the game in the end of February I've been getting random Error 90k.
They come out of the blue anywhere between 10 minutes a 3 hours apart. They're not accompanied by any lag, everything runs smoothly and then suddenly black screen with the 90k message.

It's starting to get very annoying as I can't really tank or heal dungeons and raids because I never know when the next disconnect is gonna be. Nothing else is affected either so it has to be server side, no other program I'm running that use my network has any issues.