Daniel, If you're using modpython ensure that it is built against python 2.5. You can do this by setting up the mod_python.testhandler with something like this in your apache config.

<Location /mpinfo>
   SetHandler mod_python
   PythonInterpreter main_interpreter
   PythonHandler mod_python.testhandler
</Location>

And then going to /mpinfo in your web browser. If modpython is built against 2.4, which you will find in Debian Etch, you will need to downgrade to Trac 0.10.3 and need to use the 0.10 version of the git trac plugin. Also when you built the gitplugin with 'python setup.py install' you may have seen some errors complaining that you're running python 2.4 and not 2.5.