Harmen, usually this happens when both Python (or a module) and Apache (or a module) are linked to the same library but different version (or even different compile options).
One example is expat, I'm sure Apache has it's own expat version and it's hard to make it compile with the system expat... and I beleive Python too comes with it's own version of expat. The easiest way to try is use the simplest mod_python test handler and then try to import pyexpat.
