This happens fairly often, about once every couple of hours. I will be fighting and suddenly I can't attack, at all. I can block, but can't fight back, the left mouse button just doesn't do anything. And neither do the 1-5 keys on the keyboard, or the R key. I can try and run away, but it's slow. So I die. When I respawn then I'm permanently slowed, I can't walk fast and holding shift is the same as not holding it. I have to log out and back in.