I downloaded the svn version of the trunk folder and compiled boost using VC9. After using a boost::ptr_map< unsigned int, boost::variant<int, bool, float, std::string, Resource::shrd_ptr> > I got an error at line 26 inside "boost/ptr_container/detail/serialize_ptr_map_adapter.hpp" about "ptr_container_detail::serialize_as_const" not being defined for "ptr_container_detail". Seeing as how it was however defined in boost/ptr_container/detail/serialize_reversible_cont.hpp, I copy and pasted the definition into boost/ptr_container/ptr_map_adapter.hpp (which is being included by serialize_ptr_map_adapter.hpp) and now everything seems to work. I didn't have any problems with ptr_map before, so I have no clue as to why I got this error all of a sudden, but now it works fine. Sorry if this is something which was already adressed somewhere. Regards, Thomas K.