index.php causing header problems across two separate wordpress installations.

Hey guys, I've got a strange one for you today.

I have my site http://www.itsalltrue.net that utilizes Wordpress 3.1.2 and Atahualpa 3.6.4 and a sub/add-on domain that has a separate wordpress installation with the same versions of WP & Atahualpa.

Everything has been working fine for weeks until some time between 8-9 this morning the sites started returning error messages. The main site now must have the "WWW" present while the subsite can not have the www (it must match the settings in wordpress) or it returns one of a handful of errors.

Currently, it says:

Warning: Cannot modify header information - headers already sent by (output started at /home/itsallt/public_html/wp-content/plugins/dynamic-headers/custom-header.php:97) in /home/itsallt/public_html/wp-includes/pluggable.php on line 897

But it has also blamed line 97 or 98 of index.php and will blame a different plugin if I deactive the one it's currently referencing.

I am aware that the header error apparently always implies there is an extra space somewhere, but I have NOT edited any php files on the site. I don't know where an extra space could come from.

Anyway, I've been in contact with my host and their final solution is to remove the theme entirely:

-------------------------

Thank you for your patience. Please remove and utilize a new theme as the direct line of error is being caused within the following line of code:

=========================================
<?php
/**
* Front to the WordPress application. This file doesn't do anything, but loads
* wp-blog-header.php which does and tells WordPress to load the theme.
*
* @package WordPress
*/

/**
* Tells WordPress to load the WordPress theme and output it.
*
* @var bool
*/
define('WP_USE_THEMES', true);

/** Loads the WordPress Environment and Template */
require('./wp-blog-header.php');
?>
=========================================

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I love atahualpa and there has to be a workaround for this, but I have no idea what it is.