I thought it was external to BFBC2, but it always goes away when I quit the game.
I am not running any other monitoring utilities that I know of and this is on my laptop. I _think_ that the characters are chinese and when the box pops up, hitting the direction key will change the character in the box. Alt-Enter will go back to fullscreen, but as soon as I hit any key (except the mouse) that box pops right back up and ruins the game. I usually have to quit the game and restart to make it go away. I actually got to play single player for an hour last night and it never popped up...