I am using Django 1.3.7 and python 2.7.6 on windows7 I got an error when I executing my manage.py in this line of code
import shutil, sys, virtualenv, subprocess
I just ran into this same problem. I had to pip uninstall virtualenv as a user with admin rights, then pip install virtualenv as a normal user. I think it's some kind of permissions issue if you installed virtualenv under admin rights.
pip uninstall virtualenv
pip install virtualenv