The previous build of 1.55.0 did not build with the correct zlib version (and thus the correct sub-library of iostreams did not build).

I have created a 1.55.0-build2 directory on the sourceforge page with the updated version. I've also added a note to the 1.55.0/README.md file explaining that it is incomplete, but I did not remove the prior build.

http://sourceforge.net/projects/boost/files/boost-binaries/1.55.0-build2/