PHP errors on log

Hello,

Dev version logs this PHP error (D 6.15):

/var/www/html/***/sites/all/modules/cache/engines/file.inc file on line 60 Argument 4 passed to fileCacheEngine::set() must be an array, string given, called in /var/www/html/***/sites/all/modules/cache/Cache.php on line 117 and defined

6.x-1.0-beta1 is perfectly OK.

Reporting.

Tx.

//Cache
$conf['cache_inc'] = './sites/all/modules/cache/cache.inc';
$conf['session_inc'] = './sites/all/modules/cache/session.inc';

    $conf['cache_settings'] = array(
      'engines' => array(
        'db-engine' => array(
          'engine' => 'database',
        ),
	'xc-engine' => array(
          'engine' => 'xcache',
        ),
	'fl-engine' => array(
          'engine' => 'file',
        ),
      ),
      'schemas' => array(
        'db-schema' => array(
	      'db-engine',
        ),
        'full-schema' => array(
		  'xc-engine',
		  'db-engine',
        ),
	'fl-schema' => array(
          'fl-engine',
        ),		
      ),
      'bins' => array(
        'default' => 'full-schema',
      ),
    );