Singelton MySQL DB Connect Class Issue

[xxarmoxx]

Hello, here is my current Singelton MySQL DB Connect Class:

<?php

// this is a singelton database connect class

class dbconnect {


    // Store the single instance of Database
    private static $m_pInstance;

    private function __construct() {

            // *** Database Connect ***
        $dblink = mysql_connect('localhost', 'root', 'pwd') OR die(mysql_error());

        $m_pInstance = mysql_select_db("mydb") or die(mysql_error());
            

    }


    private function __clone() {


            

    }




    public static function getInstance()
    {
        if (!self::$m_pInstance)
        {
            self::$m_pInstance = new dbconnect();
        }

        return self::$m_pInstance;
    }





}



?>

This singelton class works fine when I use SELECT statments in another class, but it doesn't work when I am trying to use INSERT statements. When I do an insert statement I get a mysql_query(): supplied argument is not a valid MySQL-Link resource error. Any ideas on whats wrong?