Hi Dan, just a quick note to say that for me (OpenSUSE 11 64 bit, g++ 4.3.1) the following has helped: #if BOOST_VERSION <= 103500 BOOST_IS_ABSTRACT(MyNamespace::MyClass) #else BOOST_SERIALIZATION_ASSUME_ABSTRACT(MyNamespace::MyClass) #endif /* Serialization traits */ You need to include . I have now moved to the Alpha/Beta version of Boost 1.36, which is quite good in my environment. Best Regards, Ruediger Dan Thomas wrote:

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Try using boost/serialization/assume_abstract.hpp

Thanks for the quick reply. I tried this change but it made no difference. I still get the same errors. I have dealt with my immediate problems by rolling back to boost 1.33.0 so I will stop pestering you about this :-)

Thanks for your help

Dan