Sorry if this has been mentioned before. But on my Lion system, there are two places where python is installed: /usr/bin and /usr/local/bin:
Directory /usr/local/bin
ipython python3-config pythonw3
ipython-qtconsole python3.1 pythonw3.1
python3 python3.1-config
and
Directory /usr/bin
python python2.6 pythonw
python-config python2.6-config pythonw2.5
python2.5 python2.7 pythonw2.6
python2.5-config python2.7-config pythonw2.7
If I use just "python" or "ipython" I end up with the new python3 system which fails with all sorts of errors. But the python2.x versions work fine.
This is a chronic difficulty with python and its package management. Probably a local expert can guide you through resolving this if you indeed have multiple, conflicting pythons. The simplest is simply to modify your PATH so that the preferred python is first.
-- Owen