Having the same issue on PC, interfaces like treasure hunter and advent calendar will open and allow you to play, and it registers options that should be visible (cutting trees etc), but entire game screen is blank.
Mine started flicking onto a black screen today but it's intermittant during gameplay. Sometimes it's every 10 secs it goes black for a second and then it'll be fine for a couple of mins then it goes a bit on/off again.
One of the times it flicked on/off there was nothing on the floor near me while I could see the screen, screen goes black and comes back within a second with a noted item on the floor, I don't even get a moment to hover on it to see what it is and the screen flickers and then comes back in less than a second without the noted item. Nobody else around. It reminds me of when you join an instance and whatever is outside the instance is gone and comes back when you step out of the instance. Except I'm not moving when it happens.
It's driving me a bit nuts as flickering screens set me off. I get the multicoloured flicker too when I'm logging on and sometimes in the lobby but I've had that for a few months now. This new black flicker is a new one.