[Boost-users] 'boost::any::holder<ValueType>' : assignment operator could not be generated

I've just installed the pre-built Boost libraries for Windows offered by boost-consulting.com. I started playing with program_options. I use the following options: options.add_options() ("help,h", "display this help message and exit") ("version,v", "output version information and exit") ("silly,s", po::value<int>(), "silly option") ; When compiling that code with Visual Studio 8.0 I get warnings about - 'boost::program_options::options_description' : assignment operator could not be generated - 'boost::any::holder<ValueType>' : assignment operator could not be generated The latter one seems to be the cause for a linking error: - unresolved external symbol "class std::basic_string boost::program_options::arg" g++ works just fine, no warnings, no link errors. Any suggestions on how to solve this? M