So, what to do? Downgrade back to 3.4.2, obviously. A quick Google search brought up this great article with some good steps to follow: http://etuts.org/manually-downgrade-wordpress/
Here are the steps, with my notes:
- Log into the administrative backend of your Wordpress installation and deactivate all your plugins (important)
- Create a backup of your site including the database for safety's sake ( or at least download all the files including those in the root directory, especially wp-config.php)
- Delete the \wp-admin and \wp-includes folders of your site either with your FTP client or through the backend cPanel of your hosting company. File Manager in cPanel is a lot quicker than through FTP.
- Find the Wordpress 3.4.2 (or whatever version you are going to downgrade to) files: http://wordpress.org/download/release-archive/ and unzip locally.
- Upload the following to your site
- root folder files
- May not be necessary, but without doing it, I ran into errors
- Remember to re-upload your old wp-config.php file, though, because it has your database settings in it.
- Log into the administrative backend of your site and it should ask you to Update Your Database. Go for it.
That's it. Most important things to remember are to make a backup of your site, overwrite the files in the root directory (which is what made it work for me) and then re-upload your wp-config.php file from your previous installation.