'CSRF verification failed." from django.contrib.comments. can you help solve it? django 1.3

I'm using django.contrib.comments and get 'CSRF token missing or incorrect.' when previewing or submitting a comment.  I have:

MIDDLEWARE_CLASSES = (

    'django.middleware.csrf.CsrfViewMiddleware',

    'django.middleware.common.CommonMiddleware',

    'django.contrib.sessions.middleware.SessionMiddleware',

    'django.contrib.auth.middleware.AuthenticationMiddleware',

    'django.contrib.messages.middleware.MessageMiddleware',

)

url(r'^comments/',              include('django.contrib.comments.urls')),

url(r'^entry/(?P<pk>\d+)/comment',      'rp2.views.entry_comment_add'),

@csrf_protect  #does not matter if this is here or not

def entry_comment_add(request, pk):

    entry = models.Entry.objects.get(pk=pk)

    assert isinstance(entry, models.Entry)

    return render(request, 'entry_comment_popup.html', {'entry':entry})

{% extends 'head-plain.html' %}

<!-- entry_comment_popup.html -->

{% load comments %}

{% block content %}

{% render_comment_form for entry %}

{% endblock %}

The HTML looks like it has the csrf security_hash in the proper place:

<form action="/comments/post/" method="post">        <div><input type="hidden" name="object_pk" value="28" id="id_object_pk" /></div>        <div><input type="hidden" name="timestamp" value="1340899354" id="id_timestamp" /></div>        <div><input type="hidden" name="security_hash" value="6e85e1c846861c80575ce435b21a855706725b00" id="id_security_hash" /></div>

...

I have read https://docs.djangoproject.com/en/dev/ref/contrib/comments/

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