the Memcache::delete(key) function is broken on several combinations of memcached+pecl-memcache combinations.
pecl-memcache 2.2.5 + memcached 1.4.2 - Memcache::delete(key) WORKS
pecl-memcache 2.2.5 + memcached 1.4.3 - Memcache::delete(key) DOES NOT WORK
pecl-memcache 2.2.5 + memcached 1.4.4 - Memcache::delete(key) WORKS
pecl-memcache 2.2.5 + memcached 1.4.5 - Memcache::delete(key) WORKS
pecl-memcache 3.0.4 + memcached 1.4.2 - Memcache::delete(key) WORKS
pecl-memcache 3.0.4 + memcached 1.4.3 - Memcache::delete(key) DOES NOT WORK
pecl-memcache 3.0.4 + memcached 1.4.4 - Memcache::delete(key) DOES NOT WORK
pecl-memcache 3.0.4 + memcached 1.4.5 - Memcache::delete(key) DOES NOT WORK