What is causing ImportError: No module named pkg_resources after upgrade of Python on os X?

I just updated Python to 2.6.4 on my Mac. I installed from the dmg package.

The binary did not seem to correctly set my Python path, so I added '/usr/local/lib/python2.6/site-packages' in .bash_profile

>>> pprint.pprint(sys.path)  
['',
'/Users/Bryan/work/django-trunk', 
'/usr/local/lib/python2.6/site-packages',  
'/Library/Frameworks/Python.framework/Versions/2.6/lib/python26.zip',  
'/Library/Frameworks/Python.framework/Versions/2.6/lib/python2.6',  
'/Library/Frameworks/Python.framework/Versions/2.6/lib/python2.6/plat-darwin',  
'/Library/Frameworks/Python.framework/Versions/2.6/lib/python2.6/plat-mac',  
'/Library/Frameworks/Python.framework/Versions/2.6/lib/python2.6/plat-mac/lib-scriptpackages',  
'/Library/Frameworks/Python.framework/Versions/2.6/lib/python2.6/lib-tk',  
'/Library/Frameworks/Python.framework/Versions/2.6/lib/python2.6/lib-old',  
'/Library/Frameworks/Python.framework/Versions/2.6/lib/python2.6/lib-dynload',  
'/Library/Frameworks/Python.framework/Versions/2.6/lib/python2.6/site-packages']

Apparently that is not all the required paths because I can't run iPython.

$ ipython  
Traceback (most recent call last):  
  File "/usr/local/bin/ipython", line 5, in <module>  
  from pkg_resources import load_entry_point  
ImportError: No module named `pkg_resources`

I've done Google searches and I can't really figure out how to install pkg_resources or make sure it's on the path.

What do I need to do to fix this?