boto.salvedad.S3ResponseError: S3ResponseError: 403 Prohibido

Estoy tratando de hacer que django suba archivos estáticos a S3, pero estoy recibiendo un error 403 forbidden, y no estoy seguro de por qué.

Traza completa:

Traceback (most recent call last):
  File "manage.py", line 14, in <module>
    execute_manager(settings)
  File "/home/levi/Projects/DoneBox/.virtualenv/local/lib/python2.7/site-packages/django/core/management/__init__.py", line 438, in execute_manager
    utility.execute()
  File "/home/levi/Projects/DoneBox/.virtualenv/local/lib/python2.7/site-packages/django/core/management/__init__.py", line 379, in execute
    self.fetch_command(subcommand).run_from_argv(self.argv)
  File "/home/levi/Projects/DoneBox/.virtualenv/local/lib/python2.7/site-packages/django/core/management/base.py", line 191, in run_from_argv
    self.execute(*args, **options.__dict__)
  File "/home/levi/Projects/DoneBox/.virtualenv/local/lib/python2.7/site-packages/django/core/management/base.py", line 220, in execute
    output = self.handle(*args, **options)
  File "/home/levi/Projects/DoneBox/.virtualenv/local/lib/python2.7/site-packages/django/core/management/base.py", line 351, in handle
    return self.handle_noargs(**options)
  File "/home/levi/Projects/DoneBox/.virtualenv/local/lib/python2.7/site-packages/django/contrib/staticfiles/management/commands/collectstatic.py", line 89, in handle_noargs
    self.copy_file(path, prefixed_path, storage, **options)
  File "/home/levi/Projects/DoneBox/.virtualenv/local/lib/python2.7/site-packages/django/contrib/staticfiles/management/commands/collectstatic.py", line 184, in copy_file
    if not self.delete_file(path, prefixed_path, source_storage, **options):
  File "/home/levi/Projects/DoneBox/.virtualenv/local/lib/python2.7/site-packages/django/contrib/staticfiles/management/commands/collectstatic.py", line 115, in delete_file
    if self.storage.exists(prefixed_path):
  File "/home/levi/Projects/DoneBox/.virtualenv/local/lib/python2.7/site-packages/storages/backends/s3boto.py", line 209, in exists
    return k.exists()
  File "/home/levi/Projects/DoneBox/.virtualenv/local/lib/python2.7/site-packages/boto/s3/key.py", line 391, in exists
    return bool(self.bucket.lookup(self.name))
  File "/home/levi/Projects/DoneBox/.virtualenv/local/lib/python2.7/site-packages/boto/s3/bucket.py", line 143, in lookup
    return self.get_key(key_name, headers=headers)
  File "/home/levi/Projects/DoneBox/.virtualenv/local/lib/python2.7/site-packages/boto/s3/bucket.py", line 208, in get_key
    response.status, response.reason, '')
boto.exception.S3ResponseError: S3ResponseError: 403 Forbidden

Contenido de settings.py:

import os
DIRNAME = os.path.dirname(__file__)
# Django settings for DoneBox project.

DEBUG = True
TEMPLATE_DEBUG = DEBUG

ADMINS = (
    # ('Your Name', '[email protected]'),
)

MANAGERS = ADMINS

DATABASES = {
    'default': {
        'ENGINE': 'django.db.backends.sqlite3', # Add 'postgresql_psycopg2', 'postgresql', 'mysql', 'sqlite3' or 'oracle'.
        'NAME': os.path.join(DIRNAME, "box.sqlite"),                      # Or path to database file if using sqlite3.
        'USER': '',                      # Not used with sqlite3.
        'PASSWORD': '',                  # Not used with sqlite3.
        'HOST': '',                      # Set to empty string for localhost. Not used with sqlite3.
        'PORT': '',                      # Set to empty string for default. Not used with sqlite3.
    }
}

# Local time zone for this installation. Choices can be found here:
# http://en.wikipedia.org/wiki/List_of_tz_zones_by_name
# although not all choices may be available on all operating systems.
# On Unix systems, a value of None will cause Django to use the same
# timezone as the operating system.
# If running in a Windows environment this must be set to the same as your
# system time zone.
TIME_ZONE = 'America/Denver'

# Language code for this installation. All choices can be found here:
# http://www.i18nguy.com/unicode/language-identifiers.html
LANGUAGE_CODE = 'en-us'

SITE_ID = 1

# If you set this to False, Django will make some optimizations so as not
# to load the internationalization machinery.
USE_I18N = True

# If you set this to False, Django will not format dates, numbers and
# calendars according to the current locale
USE_L10N = True

# Absolute filesystem path to the directory that will hold user-uploaded files.
# Example: "/home/media/media.lawrence.com/media/"
MEDIA_ROOT = ''

# URL that handles the media served from MEDIA_ROOT. Make sure to use a
# trailing slash.
# Examples: "http://media.lawrence.com/media/", "http://example.com/media/"
MEDIA_URL = "d1eyn4cjl5vzx0.cloudfront.net"

# Absolute path to the directory static files should be collected to.
# Don't put anything in this directory yourself; store your static files
# in apps' "static/" subdirectories and in STATICFILES_DIRS.
# Example: "/home/media/media.lawrence.com/static/"
STATIC_ROOT = os.path.join(DIRNAME, "static")

# URL prefix for static files.
# Example: "http://media.lawrence.com/static/"
STATIC_URL = "d280kzug7l5rug.cloudfront.net"

# URL prefix for admin static files -- CSS, JavaScript and images.
# Make sure to use a trailing slash.
# Examples: "http://foo.com/static/admin/", "/static/admin/".
ADMIN_MEDIA_PREFIX = '/static/admin/'

# Additional locations of static files
STATICFILES_DIRS = (
    # Put strings here, like "/home/html/static" or "C:/www/django/static".
    # Always use forward slashes, even on Windows.
    # Don't forget to use absolute paths, not relative paths.
    os.path.join(DIRNAME, "main", "static"),
)

# List of finder classes that know how to find static files in
# various locations.
STATICFILES_FINDERS = (
    'django.contrib.staticfiles.finders.FileSystemFinder',
    'django.contrib.staticfiles.finders.AppDirectoriesFinder',
    'django.contrib.staticfiles.finders.DefaultStorageFinder',
)

# Make this unique, and don't share it with anybody.
SECRET_KEY = '<snip>'

# List of callables that know how to import templates from various sources.
TEMPLATE_LOADERS = (
    'django.template.loaders.filesystem.Loader',
    'django.template.loaders.app_directories.Loader',
    'django.template.loaders.eggs.Loader',
)

MIDDLEWARE_CLASSES = (
    'django.middleware.common.CommonMiddleware',
    'django.contrib.sessions.middleware.SessionMiddleware',
    'django.middleware.csrf.CsrfViewMiddleware',
    'django.contrib.auth.middleware.AuthenticationMiddleware',
    'django.contrib.messages.middleware.MessageMiddleware',
)

ROOT_URLCONF = 'DoneBox.urls'

TEMPLATE_DIRS = (
    # Put strings here, like "/home/html/django_templates" or "C:/www/django/templates".
    # Always use forward slashes, even on Windows.
    # Don't forget to use absolute paths, not relative paths.
    os.path.join(DIRNAME, "main", "templates"),
    os.path.join(DIRNAME, "templates"),
    os.path.join(DIRNAME, "basic", "blog", "templates"),
)

INSTALLED_APPS = (
    'django.contrib.auth',
    'django.contrib.contenttypes',
    'django.contrib.sessions',
    'django.contrib.sites',
    'django.contrib.messages',
    'django.contrib.staticfiles',
    'django.contrib.sitemaps',
    # Uncomment the next line to enable the admin:
    'django.contrib.admin',
    # Uncomment the next line to enable admin documentation:
    'storages',
    'django.contrib.admindocs',
    'main',
    'contacts',
    'piston',
    'registration',
#    'contact_form',
    'basic',
    'basic.blog',
)

# A sample logging configuration. The only tangible logging
# performed by this configuration is to send an email to
# the site admins on every HTTP 500 error.
# See http://docs.djangoproject.com/en/dev/topics/logging for
# more details on how to customize your logging configuration.
LOGGING = {
    'version': 1,
    'disable_existing_loggers': False,
    'handlers': {
        'mail_admins': {
            'level': 'ERROR',
            'class': 'django.utils.log.AdminEmailHandler'
        }
    },
    'loggers': {
        'django.request': {
            'handlers': ['mail_admins'],
            'level': 'DEBUG',
            'propagate': True,
        },
        'django.db.backends': {
            'handlers': ['mail_admins'],
            'level': 'DEBUG',
            'propagate': True,
        }
    }
}

DEFAULT_FILE_STORAGE = 'storages.backends.s3boto.S3BotoStorage'
AWS_ACCESS_KEY_ID = '<snip>'
AWS_SECRET_ACCESS_KEY = '<snip>'
STATICFILES_STORAGE = 'storages.backends.s3boto.S3BotoStorage'
AWS_STORAGE_BUCKET_NAME = "donebox-static"
STATIC_FILES_BUCKET = "donebox-static"
MEDIA_FILES_BUCKET = "donebox-media"
ACCOUNT_ACTIVATION_DAYS = 7

EMAIL_HOST = "email-smtp.us-east-1.amazonaws.com"
EMAIL_HOST_USER = '<snip>'
EMAIL_HOST_PASSWORD = '<snip>'
EMAIL_PORT = 587
EMAIL_USE_TLS = True
TEMPLATE_CONTEXT_PROCESSORS = (
    "django.contrib.auth.context_processors.auth",
     "django.core.context_processors.debug",
     "django.core.context_processors.i18n",
     "django.core.context_processors.media",
     "django.core.context_processors.static",
     "django.contrib.messages.context_processors.messages",
     "DoneBox.main.context_processors_PandC",
     )

Contenido de los requisitos.pip:

django==1.3
django-storages==1.1.4
django-registration==0.8
django-piston==0.2.3
django-tagging==0.3.1
django-extensions==0.8
BeautifulSoup==3.2.1
boto==2.4.1
mysql-python==1.2.3
tweepy==1.9
feedparser==5.1.2
pycrypto==2.6

Una búsqueda en Google para esta excepción no muestra nada interesante. Sospecho que tengo cosas mal configuradas, aunque no estoy seguro. ¿Alguien podría indicarme la dirección correcta? Gracias por su tiempo y consideración.