Change password always shoots error

[sowh4t]

It shoots always to
if($this->parool_exists != $this->passmd5)
$this->errors[] = '<font color="red">Password is not correct</font>';
even if it is!
Really need to know what the problem is here!

<?php

class Seaded
{
  private $parool;
  private $uparool;
  private $uparool2;
  private $passmd5;

  private $errors;
  private $stoken;

  public function __construct()
  {
    $this->errors = array();

    $this->parool = $this->filter($_POST['parool']);
    $this->uparool = $this->filter($_POST['uparool']);
    $this->uparool2 = $this->filter($_POST['uparool2']);
    $this->stoken    = $_POST['stoken'];

    $this->passmd5  = md5($this->parool);
  }

  public function process()
  {
    if($this->valid_stoken() && $this->valid_data())
         $this->seaded();

    return count($this->errors)? 0 : 1;
  }

  public function filter($var)
  {
    return preg_replace('/[^a-zA-Z0-9@.]/','',$var);
  }
  public function seaded()
  {
   mysql_query("UPDATE andmed(parool) VALUES ('{$this->uparool}')");

   if(mysql_affected_rows()< 1)
     $this->errors[] = '<font color="red">Andmebaasi viga</font>';
  }

  public function parool_exists()
  {
    mysql_query("SELECT parool FROM andmed WHERE kasutajanimi='".$_SESSION['kasutajanimi']."'");
  }

  public function show_errors()
  {
    echo "";

    foreach($this->errors as $key=>$value)
      echo $value."<br>";
  }

  public function valid_data()
  {
    if($this->parool_exists != $this->passmd5)
     $this->errors[] = '<font color="red">Password is not correct</font>';
    if(empty($this->parool))
      $this->errors[] = '<font color="red">Sisestage kõik lahtrid</font>';
    if(empty($this->uparool))
      $this->errors[] = '<font color="red">Sisestage kõik lahtrid</font>';
    if(empty($this->uparool2))
      $this->errors[] = '<font color="red">Sisestage kõik lahtrid</font>';
    if($this->uparool != $this->uparool2)
      $this->errors[] = '<font color="red">Paroolid ei ühti</font>';

  return count($this->errors)? 0 : 1;
  }


  public function valid_stoken()
  {
   if(!isset($_SESSION['stoken']) || $this->stoken != $_SESSION['stoken'])
     $this->errors[] = '<font color="red">Kontrollige andmeid</font>';

   return count($this->errors)? 0 : 1;
  }
}

?>