As per summary, there's an internal copy of expat 1.x in celementtree's shared object, and its symbols are not hidden either. Loading in the same process space both libexpat (2) and python with celementtree will likely cause crashes not so easy to debug.
Easy solution: hide the symbols.
Proper solution: use the already-installed shared copy of libexpat.
I've added patches for versions 1.0.2 and 1.0.5 so they use the
already-installed shared copy of libexpat instead of the internal copy.
Versions 1.0.2-r1 and 1.0.5-r1 are in CVS which fixes this.
Thanks for reporting :-)