So this is a recent problem but has persisted almost everytime I have tried to play in the last week. The game will start fine and then in a few minutes my screen goes slightly darker, everything freezes and most of the time all the graphics and displays vanish and I can see nothing but the enviroment graphics. No people, no player models, no windows, no action bars, just background. I can still hear what's going on for several minutes and I'm told that when I type messages those still appear in the chat window.

Any ideas?