WSOD afte uninstalling the Memcache module and deleting it's folder
One of the steps to install Memcache module is to add a line in your settings.php file that specifies a module file as a cache backend.

To uninstall the Memcache module, you will also need to remove that line in settings.php.  Until then, Drupal will be attempting to load a cache backend from a file that is no longer there.