Ok, here's the dumb solution I found to make this work.
Explanation:
Upgraded Mootools is enabled on the front-end of the site but not in the backend.
How-To Steps:
1. Install and enable Mootools Control - Set Yes for "Disable mootools.js" and "Disable caption.js"
2. Install and enable "Google Ajax library" -- Only enable "Replace Mootools" and use Version 1.11
3. Go to plugins --> system --> mtupgrade and make a copy of "mootools.js" named "mtupgrade.js" and place it inside the /css folder of your website's template (templates/YOUR-TEMPLATE/css). Upload this to your live site.
4. Open libraries --> joomla --> document --> html --> renderer --> head.php (ALWAYS MAKE A BACKUP OF THE FILE BEFORE EDITING!)
5. Navigate to "// Generate script file links" and BEFORE this, paste:
$app = & JFactory::getApplication();
$template = $app->getTemplate();
if($template == "YOUR-TEMPLATE") {
$strHtml .= $tab.'<script type="text/javascript" src="templates/YOUR-TEMPLATE/css/mt-upgrade.js"></script>'.$lnEnd; }
Upload the new head.php and you're done.
