Test your Magento XML files from command line with this tool and see all errors (if any)

testXml.php

#!/usr/bin/php
<?php
/**
 * Debug an XML file
 * @author Jochem Klaver <j.klaver@drecomm.nl>
 * @link http://php.net/libxml
 */

require('app/Mage.php');
Mage::app();

if (!isset($argv) || !is_array($argv) || !isset($argv[1])) {
    die("No file given\n");
}
$xmlFile = $argv[1];
if (strtolower(substr($xmlFile, -4)) != '.xml') {
    die("File has no XML file extension\n");
}
if (!file_exists($xmlFile)) {
    die("File does not exist\n");
}
if (!is_readable($xmlFile)) {
    die("File is not readable\n");
}

$config = new Varien_Simplexml_Config();

// Set libxml to use internal error
libxml_use_internal_errors(true);
libxml_clear_errors();

if ($config->loadFile($xmlFile) && count(libxml_get_errors()) == 0) {
    die("No errors found in XML file '{$xmlFile}'\n");

} else {
    echo count(libxml_get_errors()) . " errors in XML file '{$xmlFile}'\n";

    foreach (libxml_get_errors() as $i => $error) {
        /* @var $error libXMLError */
        echo str_pad(($i+1), 3, ' ', STR_PAD_LEFT) . '. ';
        switch ($error->level) {
            case LIBXML_ERR_WARNING:
                echo "Warning";
                break;
             case LIBXML_ERR_ERROR:
                echo "Error";
                break;
            case LIBXML_ERR_FATAL:
                echo "Fatal Error";
                break;
        }
        echo ' [' . $error->code . ']';
        echo ' @ ' . (isset($error->file) && !empty($error->file) ? $error->file . ' on ' : '')
            . 'line '  . $error->line . ', column ' . $error->column;
        echo ': ' . trim($error->message);
        echo "\n";
    }
}