I'm sorry I can't provide a fully-detailed report 
here, but I'm not in a position to be able to 
reproduce the problem.

In short, I installed the Universal build of Python 
2.4.3 for the Mac downloaded from:

http://pythonmac.org/packages/py24-fat/index.html

I don't know whether this is the same as the download 
from:

http://www.python.org/download/releases/2.4.3/

Once installed, I attempted to build ctypes.

The build failed due to an assembly error (unknown 
instruction). I'm not familiar with the PPC or x86 
assembler code so couldn't do a thorough analysis.

I needed Python2.4 to work, so I found an older 
PPC-only installer and used that.

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Which version of ctypes did you try to build?

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0.9.9.6

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This might be a ctypes limitation: it might be that ctypes
doesn't support x86-OSX (atleast in this release).

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I successfully built ctypes on PPC OSX using a 
non-universal build. Also, I wasn't running on x86 OSX so 
it shouldn't have tried to build that.

I just successfully built ctypes 1.0.1 on a MacBook (ie. x86) OS X machine. I don't know whether it builds on a PPC machine.

I'm closing this bug, the problem is in ctypes installer you used.

For the record: you can build a ppc/intel only version of an extension by patching the setup.py of the project your building and adding ('-arch', 'i386') or ('-arch', 'ppc') to the extra_compile_args and extra_link_args of Extension objects (I'm typing this without looking at the documention and have probably misspelled these argument names)