yii内存缓存包含错误

我收到这个错误：

include(Memcache.php) [<a href='function.include'>function.include</a>]: failed to open stream: No such file or directory

以下是问题的完整描述：

384 * @return boolean whether the class has been loaded successfully
385      */
386     public static function autoload($className)
387     {
388         // use include so that the error PHP file may appear
389         if(isset(self::$_coreClasses[$className]))
390             include(YII_PATH.self::$_coreClasses[$className]);
391         else if(isset(self::$classMap[$className]))
392             include(self::$classMap[$className]);
393         else
394         {
395             if(strpos($className,'''')===false)
396                 include($className.'.php');
397             else  // class name with namespace in PHP 5.3
398             {
399                 $namespace=str_replace('''','.',ltrim($className,''''));
400                 if(($path=self::getPathOfAlias($namespace))!==false)
401                     include($path.'.php');
402                 else
403                     return false;
404             }
405             return class_exists($className,false) || interface_exists($className,false);
406         }
407         return true;
408     }