I've never seen those before, the missing symbols are std lib ones not Boost.Regex ones BTW. I would guess there's something unusual about how the library was built or how your app is being built. The quick solution would be to define BOOST_REGEX_NO_LIB and add all the libs/regex/src/*.cpp files directly to your project. Otherwise check that regex really was built with VC9 and not some other compiler by mistake, and check to see what defines and/or "odd" compiler options you may be using in your project.
Yes they are std errors but only pop up if I use the regex library (specifically, using regex_search is the offender). To the best of my knowledge I am not using any odd options either for my project or when I had compiled the boost library. The project is a fairly plain-vanilla console application with most options left to the default, only rather unsuspicious include directives and some optimization flags set, but the linker error also comes in debug mode. I am also using the boost threads library and others without any problems.
Boost libraries were built with sort of the default bjam toolset=msvc-9.0 --build-type=complete --build-dir=BuildDir stage, so nothing odd there as well.
Well there's clearly something odd going on because no one else has that issue ;-) Have you tried the usual last ditch resort and rebuilt the libraries? Otherwise just add the source files directly to your project (or create a regex .lib project in your IDE) and build that way. HTH, John.