"Bad marshal data" Django development server error

Got this error while insterting data into my MySQL database ``` ValueError at /admin/arbkdb/arbkcompany/ bad marshal data (unknown type code) Request Method: GET Request URL: http://[2001:6f8:1c00:18b::2]:9000/admin/arbkdb/arbkcompany/ Django Version: 1.3 Exception Type: ValueError Exception Value: bad marshal data (unknown type code) Exception Location: /usr/lib/python2.7/dist-packages/simplejson/__init__.py in <module>, line 111 Python Executable: /usr/bin/python Python Version: 2.7.2 Python Path: ['/home/ardian/.experiments/arbk', '/usr/lib/python2.7', '/usr/lib/python2.7/plat-linux2', '/usr/lib/python2.7/lib-tk', '/usr/lib/python2.7/lib-old', '/usr/lib/python2.7/lib-dynload', '/usr/local/lib/python2.7/dist-packages', '/usr/lib/python2.7/dist-packages', '/usr/lib/python2.7/dist-packages/PIL', '/usr/lib/python2.7/dist-packages/gst-0.10', '/usr/lib/python2.7/dist-packages/gtk-2.0', '/usr/lib/pymodules/python2.7', '/usr/lib/python2.7/dist-packages/ubuntu-sso-client', '/usr/lib/python2.7/dist-packages/ubuntuone-client', '/usr/lib/python2.7/dist-packages/ubuntuone-control-panel', '/usr/lib/python2.7/dist-packages/ubuntuone-couch', '/usr/lib/python2.7/dist-packages/ubuntuone-installer', '/usr/lib/python2.7/dist-packages/ubuntuone-storage-protocol'] Server time: Tue, 8 May 2012 16:15:19 -050 ``` Trackback ``` Environment: Request Method: GET Request URL: http://[2001:6f8:1c00:18b::2]:9000/admin/arbkdb/arbkcompany/ Django Version: 1.3 Python Version: 2.7.2 Installed Applications: ['admin_tools', 'admin_tools.theming', 'admin_tools.menu', 'admin_tools.dashboard', 'django.contrib.auth', 'django.contrib.contenttypes', 'django.contrib.sessions', 'django.contrib.sites', 'django.contrib.messages', 'django.contrib.staticfiles', 'arbkdb', 'south', 'django.contrib.admin'] Installed Middleware: ('django.middleware.common.CommonMiddleware', 'django.contrib.sessions.middleware.SessionMiddleware', 'django.middleware.csrf.CsrfViewMiddleware', 'django.contrib.auth.middleware.AuthenticationMiddleware', 'django.contrib.messages.middleware.MessageMiddleware') Traceback: File "/usr/lib/pymodules/python2.7/django/core/handlers/base.py" in get_response 89. response = middleware_method(request) File "/usr/lib/pymodules/python2.7/django/contrib/messages/middleware.py" in process_request 11. request._messages = default_storage(request) File "/usr/lib/pymodules/python2.7/django/contrib/messages/storage/__init__.py" in <lambda> 31. default_storage = lambda request: get_storage(settings.MESSAGE_STORAGE)(request) File "/usr/lib/pymodules/python2.7/django/contrib/messages/storage/__init__.py" in get_storage 17. mod = import_module(module) File "/usr/lib/pymodules/python2.7/django/utils/importlib.py" in import_module 35. __import__(name) File "/usr/lib/pymodules/python2.7/django/contrib/messages/storage/user_messages.py" in <module> 8. from django.contrib.messages.storage.fallback import FallbackStorage File "/usr/lib/pymodules/python2.7/django/contrib/messages/storage/fallback.py" in <module> 2. from django.contrib.messages.storage.cookie import CookieStorage File "/usr/lib/pymodules/python2.7/django/contrib/messages/storage/cookie.py" in <module> 5. from django.utils import simplejson as json File "/usr/lib/pymodules/python2.7/django/utils/simplejson/__init__.py" in <module> 111. import simplejson File "/usr/lib/python2.7/dist-packages/simplejson/__init__.py" in <module> 111. from decoder import JSONDecoder, JSONDecodeError Exception Type: ValueError at /admin/arbkdb/arbkcompany/ Exception Value: bad marshal data (unknown type code) ``` Ps. I am not sure how to describe why it came to this error because it appeard while inserting a lot of data and I don't know why This is my model data https://github.com/ardian/arbk/blob/master/arbkdb/models.py