Creating a new virtualenv gives a permissions error

Question

I'm getting the following output when running virtualenv newvenv.

Traceback (most recent call last):
  File "/usr/local/bin/virtualenv", line 5, in <module>
    from pkg_resources import load_entry_point
  File "/usr/lib/python2.7/dist-packages/pkg_resources.py", line 2727, in <module>
    add_activation_listener(lambda dist: dist.activate())
  File "/usr/lib/python2.7/dist-packages/pkg_resources.py", line 700, in subscribe
    callback(dist)
  File "/usr/lib/python2.7/dist-packages/pkg_resources.py", line 2727, in <lambda>
    add_activation_listener(lambda dist: dist.activate())
  File "/usr/lib/python2.7/dist-packages/pkg_resources.py", line 2227, in activate
    self.insert_on(path)
  File "/usr/lib/python2.7/dist-packages/pkg_resources.py", line 2334, in insert_on
    self.check_version_conflict()
  File "/usr/lib/python2.7/dist-packages/pkg_resources.py", line 2373, in check_version_conflict
    for modname in self._get_metadata('top_level.txt'):
  File "/usr/lib/python2.7/dist-packages/pkg_resources.py", line 2221, in _get_metadata
    for line in self.get_metadata_lines(name):
  File "/usr/lib/python2.7/dist-packages/pkg_resources.py", line 1209, in get_metadata_lines
    return yield_lines(self.get_metadata(name))
  File "/usr/lib/python2.7/dist-packages/pkg_resources.py", line 1201, in get_metadata
    return self._get(self._fn(self.egg_info,name))
  File "/usr/lib/python2.7/dist-packages/pkg_resources.py", line 1316, in _get
    stream = open(path, 'rb')
IOError: [Errno 13] Permission denied: '/usr/local/lib/python2.7/dist-packages/stevedore-1.5.0.egg-info/top_level.txt'

I haven't made virtualenvs in a while, but the last time I did, there was no permissions issue. virtualenv is up-to-date. While I could go messing around with permissions in the specified file in the trace, I'd rather not. Has anyone else run into similar issues with virtualenv, and if so, how did you solve them?

EDIT

The error comes up when trying to make the virtualenv in ~/venvs (Ubuntu 12.04), the same place as before the problem starting occurring, so there's no mounting problem.