Call to a member function add() on a non-object in /myhost/public_html/myproject/system/libraries/Cache/drivers/Cache_me

[eluser]Salman Khimani[/eluser]
this occurs when i call
$this->cache->memcached->save( 'mykey', array('abc'));

I have loaded
$this->load->driver('cache');

and trying to use memcache.
but that throws error
Call to a member function add() on a non-object in /myhost/public_html/myproject/system/libraries/Cache/drivers/Cache_memcached.php on line 67