OpenShift-Hosted WordPress Site Displays “The Page isn't Redirecting Properly”

I've got a WordPress site hosted on OpenShift. A plugin upgrade seems to have disabled the site entirely. I was able to reinstall a snapshot of the site from months ago. This still failed until I removed and reinstalled the plugin, Contact Form 7.

I can again access the site's public pages, though when trying to access the admin pages (using either [siteurl/wp_admin][1] or [siteurl/wp-login.php][2]) Firefox displays "The Page isn't Redirecting Properly" (other browsers have similar errors).

To avoid hack-attempts, I had changed the login URL using a plugin. Still, when attempting to login via that URL, the server reports a 404 - page not found error.

I've tried manually reinstalling WordPress as well as deactivating and uninstalling all plugins. I haven't found a way to log into the site's admin.

Any suggestions are welcomed.