Django, apache, mod_wsgi - Error: Premature end of script headers
The daemon process crashed. See comments in the mod_wsgi FAQ about what causes crashes:
http://code.google.com/p/modwsgi/wiki/FrequentlyAskedQuestions
and follow links there.
Ultimately the cause can be many things, including loading incompatible mod_python at same time, using Python C extension module that doesn't work with sub interpreters, incompatible shared library versions used by Apache and/or extension modules in PHP etc.