404 error on custom cbaseurl

I am trying to extend cbaseurl class in YII with the following code:

public function parseUrl($manager,$request,$pathInfo,$rawPathInfo)

{

    if (preg_match('%^(\w+)(/(\w+))?$%', $pathInfo, $matches))

    {

        $matches = explode('/', $pathInfo);

        $count = strlen($matches[1]);

        if ($matches[0] == 'qwin' && $count >10){                

            $matches[1] = str_replace( "_", " ", $matches[1]);

            $sql = "SELECT ans, qwin_id FROM tbl_qwin WHERE ans = :answer"; 

            $command = Yii::app()->db->createCommand($sql);

            $command->bindValue('answer', $matches[1]);

            $row = $command->queryRow();             

            return '/qwin/view/id/'.$row['qwin_id'];

        }

    }

    return false;  // this rule does not apply

}

So, for example if i request /qwin/silver_or_gold then i get Error 404 The requested page does not exist. But, the record exist with the same name without ‘_’ in my database. I don’t see where is the problem. Thanks in advance.