Error updating django 1.5 - u "'admin' is not a registered namespace - django

Question

I am upgrading django from 1.4 to 1.5 in the front and all goes well, but admin side when I try to enter the url I get this particular error, and not how to fix it, any ideas?
error:
NoReverseMatch at /admin/
u"'admin" is not a registered namespace
Request Method: GET
Request URL: http://lmgsyco.com/admin/
Django Version: 1.4.1
Exception Type: NoReverseMatch
Exception Value:
u"'admin" is not a registered namespace
Exception Location: /usr/local/lib/python2.6/dist-packages/django/template/defaulttags.py in render, line 424
Python Executable: /usr/bin/python
Python Version: 2.6.6
Urls:
from django.conf.urls.defaults import *
from django.contrib import admin
admin.autodiscover()
urlpatterns = patterns('',
url(r'^$', web_page, name='web_page'),
url(r'^login/$', 'django.contrib.auth.views.login'),
url(r'^logout/$', cerrar_sesion, name='cerrar_sesion'),
# Admin:
url(r'^admin/', include(admin.site.urls)),
# Admin documentation:
# url(r'^admin/doc/', include('django.contrib.admindocs.urls')),
)

Answer 1

I had a problem that seems related to this.
Your error is showing Django 1.4.1, while from your question you seem to be trying to use 1.5.
Check your PYTHONPATH with
env | grep PYTHONPATH
My guess is that you are pointing to the old version of Django somewhere. (In my case it was my .bashrc file. I had set up virtualenv to use Django 1.5, but .bashrc was pointing it to 1.4 , and this was getting put in first in the PYTHONPATH).