Hi Mark,
I don't think that Mac OS X comes with its own version of Gtk installed. If it had, why should macports install another one.
One of our colleagues thought that perhaps some program expects some configuration file in /usr since installing from source puts the stuff there.
I think that it is possible, by modifying the code of bibledit-gtk, to find out what's going wrong in that routine. Perhaps it can't find the screen. perhaps it's resizing the window to some odd values. It could be anything. Hopefully Friday will bring more news about it.
Yes, Linux also has crash logs - useful things.
Regards, Teus