Josh on "Accidentally changed code in theme, can't get back to it"

I was attempting to make Buddypress compatible with my theme (Nature 2.0), and followed the following instructions:

Edit the “functions.php” file in your WordPress theme.

Open up this file and add the following line to the very top right after the

<?php
include( TEMPLATEPATH . '/bp/bp-functions.php' );

By putting in this new code,I seemed to have deactivated something in the theme and I can't even access the code again to change it back. The screen comes blank when I try to even enter the wp-admin wordpress login. The situation seems dire!

I'm a super novice and should not have attempted these changes - please help with what I can do!

My site (that doesn't work is) http://www.thefreeair.com

Thanks in advance,
Josh