Developing a Django web app, I have a list of packages I need to install in a virtualenv. Say:
Django==1.3.1 --extra-index-url=http://dist.pinaxproject.com/
Given your comment to the question (where you say that executing the install for a single package works as expected), I would suggest looping over your requirement file. In bash:
#!/bin/sh while read p; do pip install $p done < requirements.pip
HTH!