When I join my server the game is running fine. I can look around with the mouse, open my inventory without issue. As soon as I press the 'W' to move, the game stops responding. I wondered if the location I was in was bugged, so I had my son kill my character. when I respawned, I had the same problem. I created a new character...same problem.
I have uninstalled the game, wiped my character data, and reinstalled, and have the same problem.
My son is not having any issues, and is able to play on our server