Another post has me convinced that the problem is that there are multiple copies of a base class extended_type_info record which I believe shouldn't occur. If you trap your debugger the serialization.dll (shared_lib) at line 58 of extened_type_info.cpp you should trap every time an extended_type_info record is "self_registered". Examination of the stack should reveal where this is being called from. I expect that the base class is being self registered from both the DLL as well as the main executable. My current thinking is that this behavior should be prohibited and detected with an exception. Other users have addressed this by tweaking the code in extended_type_info.cpp to permit multiple "self registration" of the same extended_type_info type. This eliminated their symptoms and everything seems to work. But from my understanding of the library, I believe this just hides a deeper problem. Without seeing a test program - which no one has been able to deliver, I'm just speculatiing of course. Good Luck, Robert Ramey