ImportError: No module named zlib + Virtualenv.py

Virtualenv.py complains even after I have installed the zlib development packages, restarted the terminal and rebooted the computer. What is going on with Mint14? Because I'm following the exact same setup instructions as when I was using Debian Squeeze.

linux@Mint14:~/usr-32$ sudo apt-get install zlib1g-dev
linux@Mint14:~/usr-32$ sudo apt-get install zlib1g-dbg

ENV2 - Doesn't work with downloaded Python source codes. />

linux@Mint14 ~/usr-32 $ python virtualenv.py --verbose --python=/home/linux/usr-32/py-2.4.6/bin/python2.4 /home/linux/.virtualenvs/ENV2_py24

Running virtualenv with interpreter /home/linux/usr-32/py-2.4.6/bin/python2.4

Traceback (most recent call last):
  File "virtualenv.py", line 17, in ?
    import zlib
ImportError: No module named zlib

ENV1 - But it doesn't complain when using the built-in Python version. Why is this?

linux@Mint14 ~/usr-32 $ python virtualenv.py --verbose --python=/usr/bin/python /home/linux/.virtualenvs/ENV1_py27