DOES NOT WORK WITH 4.6

I had a similar problem… maybe exactly the same as yours.
In my case, it helps me to comment 102 line with phrase if(!startsWith($dir, "/")) $dir = WP_CONTENT_DIR . "/".$dir; in the /wp-content/plugins/tx-onepager/src/WordPress/PageTemplater.php file.
The method called get_cache_key is responsible for return cache key of themes folder. If we do not comment this line, method will calculate wrong hash (will add unexpected path WP_CONTENT_DIR).
Tested on Windows where that path is starts with partition letter 🙂