I have included <boost/serialization/base_object.hpp> where it should be, it did not change anything... Anyway what is "implementing is_abstract for your compiler" ?? Jean-Noël *** its hard for me to follow what's going on here. One thing I did notice is that the I didn't see <boost/serialization/base_object.hpp> included in the places where it is used. I'm not sure if that's significant. Robert Ramey _______________________________________________ Boost-users mailing list Boost-users@lists.boost.org http://lists.boost.org/mailman/listinfo.cgi/boost-users _______________________________________________ Boost-users mailing list Boost-users@lists.boost.org http://lists.boost.org/mailman/listinfo.cgi/boost-users