I've had this one before, many months ago. Just started a battle when ALL sound went dead (I'm used to losing ambient sounds, engine noise and other random oddities, but not everything). The aircraft then appeared at the start point in black, with no other aircraft available on TAB or on the radar. Every ground target across the map could be seen at the furthest range, but with peculiarities like blue buildings on red-owned bases and vice-versa. Logged out, ran the .bat file, logged in with the clear-cache option - no change. Had to leave the battle, doubtless to the relief of the poor folk saddled with me on their team.