Emacs inserts a 'B' (ASCII 11) into the beginning of my buffer
===

And it's driving me crazy. 

My `TERM = xterm-256color`, emacs 23.3.1. I'm using Ubuntu, and this problem doesn't occur on OS X using the same dotfiles/settings. I am running it in terminal (in tmux, in bash, over SSH, on Ubuntu, iTerm2 being my emulator). 

If I open a file, e.g. `emacs init.el`, and immediately press <kbd>DOWN</kbd>, the B persists. If I don't press anything right away, my undo tree looks like this: 

    0 - initial file
    |
    0 - B inserted
    | 
    0 - B deleted

So it looks like nothing is going on. If my mark isn't at the beginning of the buffer, the B is inserted there, I think (it is harder to reproduce this). 

Any help would be MUCH appreciated. My repos are littered with commit messages like "ARGH THE B OF DOOM STRIKES AGAINaskdjasdq".

