I must have missed that thread. Thanks for the hint. I went to download the PyObjC site to download the package but I couldn't install both versions I tried because obviously I haven't installed an accurate version of Python (I didn't install any other version but the one which comes with 10.4). Did you have to install a full new Python version plus the PyObjC package or only the PyObjC package?
This version of PyObjC was compiled for Python2.3 on Tiger. It should do the trick.
PyObjC 1.3.7 installer package for Python 2.3 on Mac OS X 10.4http://prdownloads.sourceforge.net/pyobjc/pyobjc-1.3.7-py2.3-macosx10.4.zip?download