I upgraded wikimedia from 1.15 to 1.16-svn and tested brand new vector skin. it looks well/
in LocalSettings.php, I assigned cache type to CACHE_MEMCACHED. and after that PHP does not operates.
In apache log, the message is
PHP Warning: Memcached::__construct() expects parameter 1 to be string, array given in /usr/share/mediawiki/includes/ObjectCache.php on line 63, referer: <url>
PHP Fatal error: Call to a member function set_servers() on a non-object in /usr/share/mediawiki/includes/ObjectCache.php on line 64, referer: <url>
memcached version 1.4.2, and PHP-memcached was built into PHP as static library. The PHP-memcached version is 1.0, which was built against libmemcached 0.3.0. PHP version is 5.2.11.