[boost] [date_time] serialization of ptime with bcc32-5.6.4

I'm trying to serialize a ptime to an xml archive. I've included boost/date_time/posix_time/time_serialize.hpp but get an ambiguity error: [C++ Error] serialization.hpp(121): E2015 Ambiguity between 'boost::serialization::void serialize<boost::archive::xml_iarchive>(boost::archive::xml_iarchive &,boost::posix_time::ptime &,const unsigned int)' and 'boost::serialization::void serialize<boost::archive::xml_iarchive,boost::posix_time::ptime>(boost::archive::xml_iarchive &,boost::posix_time::ptime &,const unsigned int)' Is this a problem with the compiler or should this work? Thanks Russell