"undefined symbol" error from .so file after portupgrade

[Steve Franks]

I just finished a successful of portupgrade -a, so everything's
supposed to be the latest & greatest, right?  Why would I be
experiencing "dll hell" then?  These are not obscure ports...

I get the following when I import gtk in python:

   ImportError:
/usr/local/lib/python2.5/site-packages/gtk-2.0/gconf.so: Undefined
symbol "g_assertion_message_expr"

My versions:

python25-2.5.2_1
py25-gtk-2.12.

Ideas?

Steve