too long

I have Joomla! 1.7.2 Stable and when I try to Log in to administration area I get this error

 Fatal error: Call to a member function load() on a non-object in /home/shomos1/public_html/portal/libraries/joomla/user/user.php on line 822

this is the error line in my user.php

    public function load($id)
    {
        // Create the user table object

        $table  = $this->getTable();
var_dump($table);
        // Load the JUserModel object based on the user id or throw a warning.
        if (!$table->load($id)) {
            JError::raiseWarning('SOME_ERROR_CODE', JText::sprintf('JLIB_USER_ERROR_UNABLE_TO_LOAD_USER', $id));
            return false;
        }

        // Set the user parameters using the default XML file.  We might want to
        // extend this in the future to allow for the ability to have custom
        // user parameters, but for right now we'll leave it how it is.

        $this->_params->loadString($table->params);

        // Assuming all is well at this point lets bind the data
        $this->setProperties($table->getProperties());

        return true;
    }
}

I am not good in Joomla and I can't understand what is the problem there please need help what can I do to solve this problem Thanks

the default com_user component is conflicting with your component so you must rename your component files they must not have name "user" ...