[Dave]

Do the following:

1) In your includes/config.php file, make sure there's nothing in front of the opening <?php tag. No spaces, nothing.

2) If that's alright, disable all of your plugins by adding define('DISABLE_HOOKS', true); after the <?php tag in the includes/config.php file so it looks like:

PHP Code:

<?php
define('DISABLE_HOOKS', true); 

// Rest of the config file.

Is the error gone? Revert step 2 and then disable your plugins 1 by 1 until you've found which plugin is causing this.