Don’t rename the theme, because you will have the blank page. One of the plugins you have is in conflict with WordPress.
Upload the fresh copy of WordPress and keep your plugins renamed until you make this in working condition again. When all is back to normal, check the plugins and make sure that all of them are up to date and compatible with the latest WordPress.
Tonight I had similar issue with one of the test sites, there was only couple of plugins in, so I deleted both of them and the site started working. If you know what plugins you have, or better yet download plugins folder to your local machine and delete all plugins that you have on server side.
Cheers,
Emil