Python import works in interpreter, doesn't work in script Numpy/Matplotlib
You'll generally need to install numpy, matplotlib etc once for every version of python you use, as it will install itself to the specific 'python2.x/site-packages' directory. 
Is the above output generated from a 2.6 or 2.7 session? If it's a 2.6 session, then yes, pointing your PYTHONPATH at 2.7 won't work - numpy includes compiled C code (e.g. the multiarray.so file) which will have been built against a specific version of python. 
If you don't fancy maintaining two sets of packages, I'd recommend installing numpy, matplotlib etc all for version 2.7, removing that PYTHONPATH setting, and making sure that both scripts and interpreter sessions use version 2.7. 
If you want to keep both versions you'll just have to install each packages twice (and you'll probably still wnat to undo your PTYHONPATH change)
I'm on OSX Snow Leopard and I run 2.7 in my scripts and the interpreter seems to be running 2.6
Before I was able to import numpy but then I would get an error when trying to import matplotlib so I went looking for a solution and updated my PYTHONPATH variable, but I think I did it incorrectly and have now simply screwed everything up.
This is what I get when I try and import numpy in my script:

Traceback (most recent call last):
   File "./hh_main.py", line 5, in 
     import numpy
   File "/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site->packages/numpy/init.py", line 137, in 
     import add_newdocs
   File "/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site->packages/numpy/add_newdocs.py", line 9, in 
     from numpy.lib import add_newdoc
   File "/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site->packages/numpy/lib/init.py", line 4, in 
     from type_check import *
   File "/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site->packages/numpy/lib/type_check.py", line 8, in 
     import numpy.core.numeric as _nx
   File "/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site->packages/numpy/core/init.py", line 5, in 
     import multiarray
  ImportError: dlopen(/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site->packages/numpy/core/multiarray.so, 2): Symbol not found: _PyCapsule_Import
   Referenced from: /Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site->packages/numpy/core/multiarray.so
   Expected in: flat namespace
  in /Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site->packages/numpy/core/multiarray.so

Furthermore this is what I get from sys.path in the interpreter: 

['', '/Users/joshuaschneier/Documents/python_files', '/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages', '/Library/Frameworks/Python.framework/Versions/2.7/lib/python27.zip', '/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7', '/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/plat-darwin', '/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/plat-mac', '/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/plat-mac/lib-scriptpackages', '/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/lib-tk', '/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/lib-old', '/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/lib-dynload']

And this is my PYTHONPATH which I guess I updated wrong:

:/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/

Thanks for any help.