I think this crash occured because FreeCAD (from testing repository) is using coin 3.0 (libcoin60) while SoQt4 (from lenny repository) uses coin 2.0 (libsoqt4-20) Check the dependencies of your libsoqt4-20. If it shows "libcoin40" that's the problem. Both must use the same version of libcoin, so you must probably use soqt from testing too, if possible.
Cheers Yorik
