Hi, GCC-4.1.1 gives me the attached error message while compiling dynamic_image. It boils down to: dynamic_image.cpp:14: instantiated from here boost/mpl/aux_/preprocessed/gcc/template_arity.hpp:85: error: call of overloaded 'arity_helper( aux::type_wrapper< .... >,aux::arity_tag<1>)' is ambiguous boost/mpl/aux_/preprocessed/gcc/template_arity.hpp:30: note: candidates are: char (&aux::arity_helper(...))[1] boost/mpl/aux_/preprocessed/gcc/template_arity.hpp:37: note: char (&aux::arity_helper(::aux::type_wrapper<F<T1> >,aux::arity_tag<1>))[2] boost/mpl/aux_/preprocessed/gcc/template_arity.hpp:37: note: char (&aux::arity_helper(::aux::type_wrapper<F<T1> >,aux::arity_tag<1>))[2] Is this a known mpl<->gcc-4.1.1 issue? Furthermore there are some odd warnings, and I am not sure what to think about these. The code there looks a bit fishy. I tried the example with gcc-3.4.4, gcc-4.2.0-alpha20060902 and gcc-4.3.0-alpha20061111. It compiled there, but the warning remained in the gcc-4 series. Regards Andreas Pokorny