strange multiple database problem

[eluser]applepear[/eluser]
hi, there,

trust me... I know there are many discussion on this topic and tried to look at older posts on this. here is my problem.

i have two dbs, and here is how they are set up in database.php.

Code:

$active_group = 'userdb';
$active_record = TRUE;

$db['userdb']['hostname'] = 'localhost';
$db['userdb']['username'] = 'root';
$db['userdb']['password'] = '';
$db['userdb']['database'] = 'user';
$db['userdb']['dbdriver'] = 'mysql';
$db['userdb']['dbprefix'] = '';
$db['userdb']['pconnect'] = TRUE;
$db['userdb']['db_debug'] = TRUE;
$db['userdb']['cache_on'] = FALSE;
$db['userdb']['cachedir'] = '';
$db['userdb']['char_set'] = 'utf8';
$db['userdb']['dbcollat'] = 'utf8_general_ci';
$db['userdb']['swap_pre'] = '';
$db['userdb']['autoinit'] = TRUE;
$db['userdb']['stricton'] = FALSE;

$db['knowledgedb']['hostname'] = 'localhost';
$db['knowledgedb']['username'] = 'root';
$db['knowledgedb']['password'] = '';
$db['knowledgedb']['database'] = 'knowledge';
$db['knowledgedb']['dbdriver'] = 'mysql';
$db['knowledgedb']['dbprefix'] = '';
$db['knowledgedb']['pconnect'] = TRUE;
$db['knowledgedb']['db_debug'] = TRUE;
$db['knowledgedb']['cache_on'] = FALSE;
$db['knowledgedb']['cachedir'] = '';
$db['knowledgedb']['char_set'] = 'utf8';
$db['knowledgedb']['dbcollat'] = 'utf8_general_ci';
$db['knowledgedb']['swap_pre'] = '';
$db['knowledgedb']['autoinit'] = TRUE;
$db['knowledgedb']['stricton'] = FALSE;

this example involves a few model classes. user model class uses the userdb, and a few other classes uses the knowledgedb.

in user model class, DB is called by eg.

Code:

$this->db->get('user')

in eg. knowledge model class, i have

Code:

function __construct(){
        $this->kdb = $this->load->database('knowledgedb', true);
    }

    function func1(){
        ....
        $this->kdb->get('knowledge');
        ....
    }

now in the controller, i have the following code:

Code:

function __construct(){
        parent::__construct();
        $this->load->model('user');
        $this->loggedin = $this->user->is_loggedin();
        $this->load->model(array('knowledge', 'subject'));
        $this->param = $this->knowledge->func1();
    }

and so far, everything works well. then in one of the functions, i have:

Code:

function comment($kid) {
        $n = $this->knowledge->another_func();
        $n->uid = $this->user->get_userid($param1);
}

the first call works fine, but the second call gives me a Database error as the following:

Error Number: 1146

Table 'knowledge.user' doesn't exist

SELECT * FROM (`user`) WHERE `username` = 'apple'

Filename: ....\system\database\DB_driver.php

Line Number: 330

I think I did exactly as said in the user guide... how come the call to user model class is with the wrong DB if this is called after the $this->load->model('knowledge'...)?

hope the story is told clearly... thanks to you all in advance.