Magento – Magento Administration Configuration Page blank after upgrade to 1.9.1.0

I have seen many similar posts describing the problem I am experiencing, but I have been so far entirely unsuccessful in trying to resolve it. I recently upgraded to Magento CE 1.9.1.0, and now I get a blank page when navigating to System > Configuration in the back-end. The rendered page contains only empty html and body tags.

The error:

The only error that I get (in the logs or on screen with display_errors enabled in the index.php) when opening the configuration page (or any other admin page) is the following:

Fatal error: Call to undefined method Zend_Locale::getAlias() in app/code/core/Mage/Core/Model/Locale.php on line 243

Referer: http://example.com/index.php/magento/index/index/key/…/

The relevant line from Locale.php is:

$allowedAliases[Zend_Locale::getAlias($code)] = $code;

I have attempted:

• Refreshing and/or disabling all caches.
• Disabling all non-Mage modules in app/etc/local.xml (disable_local_modules), app/etc/modules (<active>false</active>), app/code/local and app/code/community (removing all files).
• Tried both PHP 5.4.16 and 5.5.21
• Comparing all files in app/ and lib/ with those from a fresh install. None were missing, but I attempted refreshing them anyway.
• Refreshing the user permissions by opening and saving the Administrator role in System > Permissions > Roles.
• Checked and re-checked file permissions, having tried both the Magento recommended perms and fully permissive (777).

System specs:

• CentOS 7
• Magento CE 1.9.1.0
• PHP 5.4.16 or 5.5.21