We have memcached running on another server just fine and the two servers are able to communicate fine through the firewall. I can telnet from web server to memcached server no problem. When I enable the memcached config in the XenForo config file, things appear to work OK, but after a few clicks, I start receiving errors. Sometimes it's completely generic (An error has occurred) and sometimes it's very specific. Here is one of the specific errors: Code: An exception occurred: Argument 2 passed to XenForo_Application::mapMerge() must be of the type array, boolean given, called in /home/devbb/public_html/library/XenForo/Dependencies/Public.php on line 304 and defined in /home/devbb/public_html/library/XenForo/Application.php on line 1174 XenForo_Application::handlePhpError() in XenForo/Application.php at line 1174 XenForo_Application::mapMerge() in XenForo/Dependencies/Public.php at line 304 XenForo_Dependencies_Public->preRenderView() in XenForo/FrontController.php at line 582 XenForo_FrontController->renderView() in XenForo/FrontController.php at line 158 XenForo_FrontController->run() in /home/devbb/public_html/index.php at line 13 Here is the XF config Code: $config['cache']['enabled'] = true; $config['cache']['frontend'] = 'Core'; $config['cache']['frontendOptions']['cache_id_prefix'] = 'bb_'; //$config['cache']['cacheSessions'] = true; $config['cache']['backend'] = 'Memcached'; $config['cache']['backendOptions'] = array( 'compression' => false, 'servers' => array( 'host' => '172.23.86.130', 'port' => 11211 ) ); Memcached has 512M available to it. Any ideas? As soon as I disable memcached in the XF config, things start working. Likewise, if I restart memcached, XF will start working again for a short time. This is currently just a dev site and I'm the only one hitting it, so I need to figure out what's going on.