Not a typical ‘Headers already sent error’

First, let me say I’ve searched the forums! It’s not a problem with wp-admin.php

The error message I’m getting is extremely long but ends with:

Warning: Cannot modify header information – headers already sent by (output started at /mnt/w0003/d33/s32/b02a8f98/www/thedogscholar.com/wp/wp-includes/deprecated.php:15) in /mnt/w0003/d33/s32/b02a8f98/www/thedogscholar.com/wp/wp-includes/pluggable.php on line 850

You can view the full error message at the admin page here.

This install is only 3 days old, how I got here was:

1. I installed WP
2. I modified my theme
3. I noticed there was an update
4. I installed the update following the instructions
5. I got the error for wp-admin, removed the spaces
6. I search, read through 25+ solutions, tried them all
7. Read the Troubleshooting guide for headers problem here
8. Posted this message 🙂

There could be something plainly obvious that I’m missing. Here’s the first 27 lines of deprecated.php:

<?php
/**
 * Deprecated functions from past WordPress versions. You shouldn't use these
 * globals and functions and look for the alternatives instead. The functions
 * and globals will be removed in a later version.
 *
 * @package WordPress
 * @subpackage Deprecated
 */

/*
 * Deprecated global variables.
 */

/**
 * The name of the Posts table
 * @global string $tableposts
 * @deprecated Use $wpdb->posts
 */
$tableposts = $wpdb->posts;

/**
 * The name of the Users table
 * @global string $tableusers
 * @deprecated Use $wpdb->users
 */
$tableusers = $wpdb->users;

It says problem should be on line 15?

Any suggestions?