This problem is related to GNUstep's Distributed Objects implementation which can use ffcall or libffi. On most architecture, libffi is the preferred choice.
Unfortunately, Ubuntu's GNUstep packages are linked against ffcall so you must re-install the version linked against libffi if you experience crashes of your sogod processes as soon as you are trying to perform an operation (Web or DAV).
See http://packages.ubuntu.com/jaunty/libgnustep-base1.16-libffi for details. To install that package on Ubuntu, simply do:
apt-get install libgnustep-base1.16-libffi
and then, recompile SOPE and SOGo.