Saving Articles gives Internal Server Error - Joomla! Forum - community, help and support

i'm hosting joomla site ipage. i'm trying edit article via backend , when save internal server error. many other pages within admin backend gives me same error when try save. example i'm trying take site offline maintenance via site->global configuration , click site offline radio button. trying save after gives error below well. start troubleshoot this?
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internal server error
the server encountered internal error or misconfiguration , unable complete request.

please contact server administrator, cgiadmin@yourhostingaccount.com , inform them of time error occurred, , might have done may have caused error.

more information error may available in server error log.

server error logs showed error:
20120819t023022: <mydomain>/administrator/index.php php fatal error: call member function add() on non-object in /hermes/bosweb26b/b2209/ipg.<mydomain>/libraries/joomla/cache/storage/memcache.php on line 435

i looked specific error in forums , other people have run too. per post same error (shown below), manually changed configuration.php file variable $cache_handler = 'file' instead of 'memcache' , fixed issues having saving things in backend.
***** manual signatures not allowed *****
go configuration.php , change setting.
public $caching = '0';
public $cache_handler = 'file';
public $cachetime = '15';

instead of:-
public $caching = '0';
public $cache_handler = 'memcache';
public $cachetime = '30';
public $memcache_persist = '1';
public $memcache_compress = '0';
public $memcache_server_host = 'mem';
public $memcache_server_port = '11211';

this manually change 'file' 'memcache' fix problem. if can't change in settings.
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