Without warning, the game will suddenly freeze up and lock for upwards of 10-15 seconds. The mouse and keyboard lock in place, and can only alt-tab out. Background music keeps playing, but no other effects as the game is currently 'paused'. CPU usage halves during this freeze, and GPU and Wifi both drop nearly to zero during it, memory and harddrive usage are not affected. Afterwards, when it resumes, the game just flashes forward as if everything was normal, or in the case of singleplayer games, resumes as if it was paused. Slightly different behavior is exhibited in the menus, stuttering 2-5 times over the duration and updating the cursor position, but not button clicks seemingly. Again, music continues, but the background blinks forward with the cursor like there's something bottle-necking it, but whatever it is isn't hardware related.
I'm out of ideas. This problem was persistent from the second beta, and sometimes it affects the other players, sometimes not. Damned if I know what the hell is going on.