Hello Boosters, I tried searching for previous discussion of this issue, and did not locate anything; my apologies if I missed it... I found a problem in the boost_1_33_1 file config/compiler/vacpp.hpp for version 6.0 of that compiler. I was getting the classic error message from the xlC linker caused by undefined class-level static variables: ld: 0711-317 ERROR: Undefined symbol: boost::details::pool::ct_lcm<8,8>::value ld: 0711-317 ERROR: Undefined symbol: boost::pool<boost::default_user_allocator_new_delete>::min_alloc_size After rooting around a bit, I ended up setting the configuration switch BOOST_NO_INCLASS_MEMBER_INITIALIZATION for v6.0. It is already set for v5.2 and earlier versions, but it was not set for v6.0 . In any case, enabling this switch (and thus using enums instead of class-static variables), the compiler problems ceased. How do I make sure this gets added to the boost config files? - Bryan E