_png_set_palette_to_rgb not found when installing on OSX

I have installed, using Fink commander, freetype2 2.1.3-22.

I have then downloaded the zips of
libpng-1.2.33
matplotlib-0.98.3
ipython-0.8.4
and then built and installed them.

when I run ipython -pylab the ipython aborts with the following:

Traceback (most recent call last):
   File "/Library/Frameworks/Python.framework/Versions/Current/bin/ipython", line 27, in <module>
     IPython.Shell.start().mainloop()
   File "/Library/Frameworks/Python.framework/Versions/2.5/lib/python2.5/site-packages/IPython/Shell.py", line 1220, in start
     return shell(user_ns = user_ns)
....etc
ImportError: dlopen(/Library/Frameworks/Python.framework/Versions/2.5/lib/python2.5/site-packages/matplotlib/_png.so, 2): Symbol not found: _png_set_palette_to_rgb
   Referenced from: /Library/Frameworks/Python.framework/Versions/2.5/lib/python2.5/site-packages/matplotlib/_png.so
   Expected in: dynamic lookup

I'm running on OSX 10.4.11. I assume the problem is with the line
ImportError: dlopen(/Library/Frameworks/Python.framework/Versions/2.5/lib/python2.5/site-packages/matplotlib/_png.so, 2): Symbol not found: _png_set_palette_to_rgb

Does anyone have any idea what is wrong here?

Thanks,

Garvin.

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