I went to the trouble of using a default WP template and a single plugin on our staging site – Compress JPEG & PNG images. No problem with version 2.2.4; the same problem with 2.2.5 – HTTP error.
We use WP Engine as a host, and fortunately I had an opportunity to restore to version 2.2.4 without loosing any work, as picked it up soon after the update. Looking at alternatives now while using 2.2.4.