Thanks for the response. I'd have continued the thread, but I didn't get the original emails from the list to reply to. I tried an explicit registration, with the same results. Also, I did step into the code where the EXPORT macros were being called, and I verified that the pertinent classes were registered in the boost::serialization::detail::ktmap, at least (not sure about the tkmap). It seems like it just doesn't find the class in the oserialization file where the exception is thrown. The serialization is invoked in a const public class method, via "oa << this;" Is there anything tricky you might be aware of that could cause the type comparisons to fail? Could I potentially be missing something in my class? Unfortunately, the project is quite large and it'd fairly difficult to strip out everything and add it back in incrementally.