Messed up keys in vim when running inside tmux

I have been playing with tmux and I'm loving it. However, there's an annoying issue when running vim inside it.

Somehow the arrow keys get remapped, but only on certain times, like when firing up Command-T, if I try to scroll down the file list, the command is cancelled and I'm thrown into insert mode, and depending on the arrow key I pressed, an A, B, C, or D is inserted.

If I use the arrows to move through a buffer for example, they work properly.

Any ideas?

Thanks!

I simply added set -g default-terminal "xterm" to my .tmux.conf

This made tmux use xterm instead of screen, so life is beautiful and I don't need to worry about stomping on keybindings.

Finally I found my answer here: when running screen on OSX, command+r messes up arrow keys in vim across all screens

The weird thing is I only added ONE mapping to my .vimrc file:

map <Esc>[B <Down>

But that single mapping makes ALL the arrow keys work properly...