Virtualenv retour a 'Aucun fichier ou répertoire...' erreur

La commande virtualenv --no-site-packages env/ génère l'erreur suivante trace de la pile:

    The --no-site-packages flag is deprecated; it is now the default behavior.
New python executable in env/bin/python
Installing setuptools.............done.
Installing pip...
  Error [Errno 2] No such file or directory while executing command /home/zach/School/CS...env/bin/easy_install /usr/local/lib/pytho...pport/pip-1.1.tar.gz
...Installing pip...done.
Traceback (most recent call last):
  File "/usr/local/bin/virtualenv", line 9, in <module>
    load_entry_point('virtualenv==1.7.1.2', 'console_scripts', 'virtualenv')()
  File "/usr/local/lib/python2.7/dist-packages/virtualenv.py", line 928, in main
    never_download=options.never_download)
  File "/usr/local/lib/python2.7/dist-packages/virtualenv.py", line 1042, in create_environment
    install_pip(py_executable, search_dirs=search_dirs, never_download=never_download)
  File "/usr/local/lib/python2.7/dist-packages/virtualenv.py", line 640, in install_pip
    filter_stdout=_filter_setup)
  File "/usr/local/lib/python2.7/dist-packages/virtualenv.py", line 966, in call_subprocess
    cwd=cwd, env=env)
  File "/usr/lib/python2.7/subprocess.py", line 679, in __init__
    errread, errwrite)
  File "/usr/lib/python2.7/subprocess.py", line 1239, in _execute_child
    raise child_exception
OSError: [Errno 2] No such file or directory

J'utilise Ubuntu 11.10 et Python 2.7.

EDIT:
Pensé à elle.

J'ai d'abord installé avec le pip, j'ai donc désinstallé via pip et réinstallé via apt-get.