64 bit COM server not instantiated from 32 bit COM server when boost/python.hpp included

I have two COM servers (exe): a 64 bit one and a 32 bit one. The 32 bit COM server instantiates (CoCreateInstance) the 64 bit COM server. This succeeds as long as the 64 bit COM server does not include boost/python.hpp. However, once I include boost/python.hpp in the 64 bit COM server project, CoCreateInstance fails: 0x80080005 ('Server execution failed') is returned as HRESULT. Starting the 64 bit COM server stand-alone while boost/python.hpp is included works fine though.

To summarize:

• 64 bit COM server does not include boost/python.hpp: CoCreateInstance of 64 bit COM server from 32 bit server works fine

• 64 bit COM server includes boost/python.hpp: CoCreateInstance of 64 bit COM server from 32 bit server fails with error 0x80080005 ('Server execution failed')

• 64 bit COM server includes boost/python.hpp and is started stand-alone (without starting 32 bit COM server): 64 bit COM server starts up without any problem

• 64 bit COM server includes boost/python.hpp and is started before 32 bit COM server is started: CoCreateInstance of 64 bit COM server from 32 bit server fails with error 0x80080005 ('Server execution failed')

I am stuck and hopefully somebody can help me here. Why does including boost/python.hpp in this situation result in an error? Any suggestions or concrete solution?