If you're having problems with Memcached, then open object-cache.php and replace the wp_cache_set() function with the following:
function wp_cache_set($key, $data, $flag = '', $expire = 0) {
global $wp_object_cache;
if ( defined('WP_INSTALLING') == false )
return $wp_object_cache->set($key, $data, $flag, $expire);
else
return true;
}
Memcached isn't officially supported by us by this may fix problems when registering new blogs.
