Python cannot get form with urllib or mechanize

I am trying to fill out and submit a form using Python, but I cannot get the resulting page. I tried using the mechanize and urllib / urllib2 methods to publish the form, but both of them run into problems.

The form I'm trying to find is here: http://zrs.leidenuniv.nl/ul/start.php . The page is in Dutch, but this is not relevant to my problem. You may notice that the action of the form is redirected to http://zrs.leidenuniv.nl/ul/query.php .

First of all, this is the urllib / urllib2 method that I tried:

import urllib, urllib2
import socket, cookielib

url = 'http://zrs.leidenuniv.nl/ul/start.php'
params = {'day': 1, 'month': 5, 'year': 2012, 'quickselect' : "unchecked",
          'res_instantie': '_ALL_', 'selgebouw': '_ALL_', 'zrssort': "locatie",
          'submit' : "Uitvoeren"}
http_header = {  "User-Agent" : "Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/535.11 (KHTML, like Gecko) Chrome/17.0.963.46 Safari/535.11",
                 "Accept" : "text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8",
                 "Accept-Language" : "nl-NL,nl;q=0.8,en-US;q=0.6,en;q=0.4" }

timeout = 15
socket.setdefaulttimeout(timeout)

request = urllib2.Request(url, urllib.urlencode(params), http_header)
response = urllib2.urlopen(request)

cookies = cookielib.CookieJar()
cookies.extract_cookies(response, request)
cookie_handler = urllib2.HTTPCookieProcessor(cookies)
redirect_handler = urllib2.HTTPRedirectHandler()

opener = urllib2.build_opener(redirect_handler, cookie_handler)

response = opener.open(request)
html = response.read()

, html, , , . , , .

, mechanize . , ParseError :

import mechanize

url = 'http://zrs.leidenuniv.nl/ul/start.php'
br = mechanize.Browser()
response = br.open(url)
br.select_form(nr = 0)

: "ParseError: " - "char ". , DOCTYPE, , . .

.